Hindawi Publishing Corporation Journal of Applied Mathematics Volume 2013, Article ID 127615, 7 pages http://dx.doi.org/10.1155/2013/127615 Research Article Fekete-Szegy Inequality for a Subclass of π-Valent Analytic Functions Mohsan Raza,1 Muhammad Arif,2 and Maslina Darus3 1 Department of Mathematics, Government College University Faisalabad, Faisalabad, Punjab 38000, Pakistan Department of Mathematics, Abdul Wali Khan University Mardan, Mardan, Khyber Pakhtunkhwa 23200, Pakistan 3 School of Mathematical Sciences, Faculty of Science and Technology Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor D. Ehsan, Malaysia 2 Correspondence should be addressed to Muhammad Arif; marifmaths@yahoo.com Received 18 January 2013; Accepted 11 April 2013 Academic Editor: Mina Abd-El-Malek Copyright © 2013 Mohsan Raza et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The main object of this paper is to study Fekete-SzegoΜ problem for the class of π-valent functions. Fekete-SzegoΜ inequality of several classes is obtained as special cases from our results. Applications of the results are also obtained on the class defined by convolution. 1. Introduction and Preliminaries Let π΄ π denote the class of functions π(π§) of the form ∞ π (π§) = π§π + ∑ ππ π§π , (π ∈ N = {1, 2, 3, . . .}) , π=π+1 (1) which are analytic in the open unit disk πΈ. Also, π΄ 1 = π΄, the usual class of analytic functions defined in the open unit disk πΈ = {π§ : |π§| < 1}. Let π(π§) and π(π§) be analytic in πΈ. We say that the function π is subordinate to the function π and write π(π§) βΊ π(π§), if and only if there exists Schwarz function π€, analytic in πΈ such that π€(0) = 0, |π€(π§)| < 1 for π§ ∈ πΈ, and π(π§) = π(π€(π§)). In particular, if π is univalent in πΈ, then we have the following equivalence: π (π§) βΊ π (π§) ⇐⇒ π (0) = π (0) , π (πΈ) ⊂ π (πΈ) . (2) For any two analytic functions π(π§) of the form (1) and π(π§) with π§πσΈ (π§) βΊ π (π§) , ππ (π§) π§ ∈ πΈ. (5) The class ππ∗ (π) was defined and studied by Ali et al. [1]. They obtained the Fekete-SzegoΜ inequality for functions in the class ππ∗ (π). The class π1∗ (π) coincides with the class π∗ (π) discussed by Ma and Minda [2]. Owa [3] introduced a subclass of πvalently Bazilevic functions π»π (π΄, π΅, πΌ, π½). A function π ∈ π΄ π is said to be in the class π»π (π΄, π΅, πΌ, π½) if and only if (1 − π½) ( π(π§) πΌ π§πσΈ (π§) π (π§) πΌ 1 + π΄π§ + π½ , ) ) βΊ ( π§π ππ (π§) π§π 1 + π΅π§ π§ ∈ πΈ, (6) ∞ π (π§) = π§π + ∑ ππ π§π , π§ ∈ πΈ, π=π+1 (3) the convolution (Hadamard product) is given by π Let π(π§) be an analytic function with positive real part on πΈ with π(0) = 1, πσΈ (0) > 0, which maps the unit disk πΈ onto a region starlike with respect to 1 which is symmetric with respect to the real axis. Denote by ππ∗ (π) the class of functions π analytic in πΈ for which ∞ π (π ∗ π) (π§) = π§ + ∑ ππ ππ π§ , π=π+1 π§ ∈ πΈ. (4) where −1 ≤ π΅ < π΄ ≤ 1, πΌ ≥ 0, and 0 ≤ π½ ≤ 1. We now define the following subclass of analytic functions. Definition 1. Let π(π§) be a univalent starlike function with respect to 1 which maps the unit disk πΈ onto a region in the right half-plane which is symmetric with respect to the real 2 Journal of Applied Mathematics axis with π(0) = 1 and πσΈ (0) > 0. A function π ∈ π΄ π is in the class ππ,π,πΌ,π½ (π) if 1− πΌ π (π§) 2 2 + { (1 − π½) ( π ) π π π§ π§πσΈ (π§) π (π§) πΌ +π½ ) } βΊ π (π§) , ( ππ (π§) π§π We need the following results to obtain our main results. Lemma 3 (see [1]). Let Ω be the class of analytic functions π€, normalized by π€(0) = 0, satisfying condition |π€(π§)| < 1. If π€ ∈ Ω and π€(π§) = π€1 π§ + π€2 π§2 + ⋅ ⋅ ⋅ , π§ ∈ πΈ, then (7) −π‘, { { σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨π€2 − π‘π€1 σ΅¨σ΅¨ ≤ {1, σ΅¨ { σ΅¨ {π‘, where 0 ≤ π½ ≤ 1, πΌ ≥ 0, and π > 0. Definition 2. A function π ∈ π΄ π is in the class ππ,π,πΌ,π½,π (π) if πΌ (π ∗ π) (π§) 2 2 ) 1 − + { (1 − π½) ( π π π§π σΈ +π½ πΌ π§(π ∗ π) (π§) (π ∗ π) (π§) ( ) } βΊ π (π§) , π§π π (π ∗ π) (π§) (8) where 0 ≤ π½ ≤ 1, πΌ ≥ 0, and π > 0. In other words, a function π ∈ π΄ π is in the class ππ,π,πΌ,π½,π (π) if (π ∗ π)(π§) ∈ ππ,π,πΌ,π½ (π). We have the following special cases. (i) ππ,2,1,1 (π) coincides with the class and studied by Ali et al. [1]. ππ∗ (π) introduced (ii) For π = 1, π = 2, and π½ = 1, we have the class π΅πΌ (π) introduced and studied by Ravichandran et al. [4]. (iii) For π = 2 and π(π§) = (1 + π΄π§)/(1 + π΅π§), the class ππ,2,πΌ,π½ (π) reduces to π»π (π΄, π΅, πΌ, π½) introduced and studied by Owa [3]. (iv) For π(π§) = (1 + (1 − 2πΎ)π§)/(1 − π§), the class ππ,2,πΌ,1 (π) reduces to the class π΅π (πΌ, πΎ) defined as π§π (π§) π (π§) ) ) > πΎ, π΅π (πΌ, πΎ) = {π ∈ π΄ π : Re ( ( ππ (π§) π§π (9) (v) For π(π§) = (1 + (1 − 2πΎ)π§)/(1 − π§), the class ππ,2,πΌ,0 (π) is defined as π (π§) πΌ ) > πΎ, 0 ≤ πΎ < 1, π§ ∈ πΈ} . π§π (10) (vi) π1,2,0,1 (π) = π∗ (π) is investigated by Ma and Minda [2]. (vii) For π(π§) = (1 + (1 − 2πΎ)π§)/(1 − π§), the class π1,2,1,0 (π) reduces to the class π΅πΎ = {π ∈ π΄ 1 : Re studied by Chen [5]. σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨π€2 − π‘π€12 σ΅¨σ΅¨σ΅¨ + (1 + π‘) σ΅¨σ΅¨σ΅¨σ΅¨π€1 σ΅¨σ΅¨σ΅¨σ΅¨2 ≤ 1, σ΅¨ σ΅¨ σ΅¨σ΅¨ σ΅¨ σ΅¨σ΅¨π€2 − π‘π€12 σ΅¨σ΅¨σ΅¨ + (1 − π‘) σ΅¨σ΅¨σ΅¨σ΅¨π€1 σ΅¨σ΅¨σ΅¨σ΅¨2 ≤ 1, σ΅¨ σ΅¨ π (π§) > πΎ} . π§ −1 < π‘ ≤ 0, 0 < π‘ < 1. (13) Lemma 4 (see [6, (7), page 10]). If π€ ∈ Ω and π€(π§) = π€1 π§ + π€2 π§2 + ⋅ ⋅ ⋅ , π§ ∈ πΈ, then σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨π€2 − π‘π€12 σ΅¨σ΅¨σ΅¨ ≤ max {1; |π‘|} , σ΅¨ σ΅¨ (14) for any complex number π‘. The result is sharp for the functions π€(π§) = π§2 or π€(π§) = π§. Lemma 5 (see [7]). If π€ ∈ Ω, then for any real number π1 and π2 , the following sharp estimate holds: σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨π€3 + π1 π€1 π€2 + π2 π€13 σ΅¨σ΅¨σ΅¨ ≤ π» (π1 , π2 ) , σ΅¨ σ΅¨ (15) where π» (π1 , π2 ) 0 ≤ πΎ < 1, π§ ∈ πΈ} . {π ∈ π΄ π : Re ( (12) For π‘ ≤ −1 or π‘ ≥ 1, the equality holds, if and only if π€(π§) = π§ or one of its rotation. For −1 ≤ π‘ ≤ 1, the equality holds, if π€(π§) = π§2 or one of its rotation. the equality holds for π‘ = −1, if and only if π€(π§) = π§((π + π§)/(1 + ππ§)) (0 ≤ π ≤ 1) or one of its rotation, while for π‘ = 1, the equality holds, if and only if π€(π§) = −π§((π + π§)/(1 + ππ§)) (0 ≤ π ≤ 1) or one of its rotation. The above upper bound for −1 < π‘ < 1 is sharp, and it can be improved as follows: πΌ σΈ π‘ < −1, −1 ≤ π‘ ≤ 1, π‘ > 1. (11) 1, { { { { (π1 , π2 ) ∈ π·1 ∪ π·2 , { { { σ΅¨σ΅¨ σ΅¨σ΅¨ { { π σ΅¨ { σ΅¨ 2 σ΅¨σ΅¨ , { { 7 { { { { (π1 , π2 ) ∈ β π·π , { { { π=3 { { 1/2 { σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1 { 2 σ΅¨ σ΅¨ { σ΅¨ σ΅¨ σ΅¨ σ΅¨ { ) , (σ΅¨π σ΅¨ + 1) ( σ΅¨σ΅¨ σ΅¨σ΅¨ { { { 3 σ΅¨ 1σ΅¨ 3 (σ΅¨σ΅¨π1 σ΅¨σ΅¨ + 1 + π2 ) ={ { { (π1 , π2 ) ∈ π·8 ∪ π·9 , { 1/2 { { π12 − 4 π12 − 4 { 1 { { ( ) ( , ) π { { 3 2 π12 − 4π2 3 (π2 − 1) { { { { { (π1 , π2 ) ∈ π·10 ∪ π·11 \ {±2, 1} , { { { 1/2 σ΅¨σ΅¨ σ΅¨σ΅¨ { { σ΅¨σ΅¨π1 σ΅¨σ΅¨ − 1 2 σ΅¨σ΅¨ σ΅¨σ΅¨ { { ) , (σ΅¨π σ΅¨ − 1) ( σ΅¨σ΅¨ σ΅¨σ΅¨ { { { 3 σ΅¨ 1σ΅¨ 3 (σ΅¨σ΅¨π1 σ΅¨σ΅¨ − 1 − π2 ) { { { (π1 , π2 ) ∈ π·12 . (16) Journal of Applied Mathematics 3 The extremal function up to the rotations is of the form π€ (π§) = π§3 , π€ (π§) = π€0 (π§) = π€ (π§) = π§, π§ ([(1 − π) π2 + ππ1 ] − π1 π2 π§) , 1 − [(1 − π) π1 + ππ2 ] π§ π€ (π§) = π€1 (π§) = π§ (π‘1 − π§) , 1 − π‘1 π§ π€ (π§) = π€2 (π§) = π§ (π‘2 + π§) , 1 + π‘2 π§ σ΅¨σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨π1 σ΅¨σ΅¨ = σ΅¨σ΅¨π2 σ΅¨σ΅¨ = 1, π0 , 2 π‘0 = ( 3 (π2 − 1) (π12 − 4π2 ) π‘1 = ( π ± π (17) π= , 2π π0 , 2 2π2 (π12 + 2) − 3π12 1/2 ) , 1/2 σ΅¨σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨π1 σ΅¨σ΅¨ + 1 ) , σ΅¨σ΅¨ σ΅¨σ΅¨ 3 (σ΅¨σ΅¨π1 σ΅¨σ΅¨ + 1 + π2 ) π0 π1 = ( 2 2 π2 (π12 + 8) − 2 (π12 + 2) 2π2 (π12 + 2) − σ΅¨ σ΅¨ π·9 = { (π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≥ 2, 3π12 σ΅¨ σ΅¨ σ΅¨ σ΅¨ 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1) 1 2 ≤ π2 ≤ (π + 8)} , σ΅¨ σ΅¨ 12 1 π12 + 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 4 σ΅¨ σ΅¨ π·11 = { (π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≥ 4, σ΅¨ σ΅¨ σ΅¨ σ΅¨ σ΅¨ σ΅¨ σ΅¨ σ΅¨ 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1) 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ − 1) ≤ π }, ≤ σ΅¨ σ΅¨ σ΅¨ σ΅¨ 2 π12 + 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 4 π12 − 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 4 σ΅¨ σ΅¨ π·12 = { (π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≥ 4, σ΅¨ σ΅¨ σ΅¨ σ΅¨ 2 σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ − 1) 2 σ΅¨ σ΅¨ ≤ π2 ≤ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ − 1)} . σ΅¨σ΅¨ σ΅¨σ΅¨ 2 3 π1 − 2 σ΅¨σ΅¨π1 σ΅¨σ΅¨ + 4 1/2 σ΅¨σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨π1 σ΅¨σ΅¨ − 1 π‘2 = ( σ΅¨σ΅¨ σ΅¨σ΅¨ ) , 3 (σ΅¨σ΅¨π1 σ΅¨σ΅¨ − 1 − π2 ) cos 2 σ΅¨ σ΅¨ 4 σ΅¨ σ΅¨ 3 σ΅¨ σ΅¨ − (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1) ≤ π2 ≤ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1) − (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1)} , 3 27 σ΅¨ σ΅¨ π·10 = { (π1 , π2 ) : 2 ≤ σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≤ 4, π1 = π‘0 − π−ππ0 /2 (π β π) , π = √ 1 − π‘02 sin2 (18) 2. Main Results ). The sets π·π , π = 1, 2, . . . , 12 are defined as follows: Theorem 6. Let π(π§) = 1 + π΅1 π§ + π΅2 π§2 + π΅3 π§3 + ⋅ ⋅ ⋅ , where π΅π , π are real with π΅1 > 0 and π΅2 ≥ 0. Let 2 π1 = σ΅¨ σ΅¨ 1 σ΅¨ σ΅¨ π·1 = {(π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≤ , σ΅¨σ΅¨σ΅¨π2 σ΅¨σ΅¨σ΅¨ ≤ 1} , 2 π·2 = {(π1 , π2 ) : 1 σ΅¨σ΅¨ σ΅¨σ΅¨ ≤ σ΅¨π σ΅¨ ≤ 2, 2 σ΅¨ 1σ΅¨ σ΅¨ σ΅¨ σ΅¨ σ΅¨ 2 σ΅¨σ΅¨π σ΅¨σ΅¨ (σ΅¨σ΅¨π σ΅¨σ΅¨ + 1) 2 σ΅¨ σ΅¨ − (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1) ≤ π2 ≤ σ΅¨2 1 σ΅¨ σ΅¨σ΅¨σ΅¨ 1 σ΅¨σ΅¨σ΅¨ }, 3 π1 + 2 σ΅¨σ΅¨π1 σ΅¨σ΅¨ + 4 π2 = −π−ππ0 /2 (ππ ± π) , π = π‘0 cos π·8 = {(π1 , π2 ) : 1 σ΅¨σ΅¨ σ΅¨σ΅¨ ≤ σ΅¨π σ΅¨ ≤ 2, 2 σ΅¨ 1σ΅¨ 4 σ΅¨σ΅¨ σ΅¨σ΅¨ 3 σ΅¨ σ΅¨ (σ΅¨π σ΅¨ + 1) − (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1) ≤ π2 ≤ 1} , 27 σ΅¨ 1 σ΅¨ × {2 (π΅2 − π΅1 ) − πππ΅12 1 2 σ΅¨ σ΅¨ π·6 = {(π1 , π2 ) : 2 ≤ σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≤ 4, π2 ≥ (π + 8)} , 12 1 2 σ΅¨ σ΅¨ σ΅¨ σ΅¨ π·7 = {(π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≥ 4, π2 ≥ (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ − 1)} , 3 (πΌ − 1) (πΌπ + 2π½) 2(πΌπ + π½) 2 }, 2 π2 = (πΌπ + π½) πππ΅12 (πΌπ + 2π½) × {2 (π΅2 + π΅1 ) − πππ΅12 σ΅¨ σ΅¨ 1 σ΅¨ σ΅¨ π·3 = {(π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≤ , σ΅¨σ΅¨σ΅¨π2 σ΅¨σ΅¨σ΅¨ ≤ −1} , 2 2 σ΅¨ σ΅¨ σ΅¨ σ΅¨ 1 π·4 = {(π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≥ , π2 ≤ − (σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ + 1)} , 2 3 σ΅¨ σ΅¨ π·5 = {(π1 , π2 ) : σ΅¨σ΅¨σ΅¨π1 σ΅¨σ΅¨σ΅¨ ≤ 2, π2 ≥ 1} , (πΌπ + π½) πππ΅12 (πΌπ + 2π½) (πΌ − 1) (πΌπ + 2π½) 2(πΌπ + π½) 2 }, 2 π3 = (πΌπ + π½) πππ΅12 (πΌπ + 2π½) × {2π΅2 − πππ΅12 Φ (π, πΌ, π½, π) = (πΌ − 1) (πΌπ + 2π½) 2 2(πΌπ + π½) (πΌπ + 2π½) (2π + πΌ − 1) 2 2(πΌπ + π½) }, . (19) 4 Journal of Applied Mathematics If π(π§) is of the form (1) and belongs to the class ππ,π,πΌ,π½ (π), then σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ πππ΅12 ππ { − (π΅ Φ (π, πΌ, π½, π)) , { 2 { { 2 2 (πΌπ + 2π½) { { { { π < π1 , { { { { { { πππ΅1 , π1 ≤ π ≤ π2 , ≤{ { 2 (πΌπ + 2π½) { { { { { πππ΅12 ππ { { { − (π΅ − Φ (π, πΌ, π½, π)) , 2 { { 2 { { 2 (πΌπ + 2π½) π > π2 . { where π»(π1 , π2 ) is defined in Lemma 3 and π1 = 2π΅2 πππ΅1 (1 − πΌ) (πΌπ + 3π½) + , π΅1 2 (πΌπ + π½) (πΌπ + 2π½) π2 = πππ΅1 2 (πΌ − 1) (2πΌ − 1) (πΌπ + 3π½) π΅3 +( ) 3 π΅1 2 6(πΌπ + π½) (20) + Proof. Since π ∈ ππ,π,πΌ,π½ (π), therefore we have for a Schwarz function π€ (π§) = π€1 π§ + π€2 π§2 + ⋅ ⋅ ⋅ , 1− 2 π΅ (πΌπ + π½) 1 (2 (1 − 2 ) πππ΅1 π΅1 (πΌπ + 2π½) πππ΅1 σ΅¨2 σ΅¨ + (2π + πΌ − 1) ) σ΅¨σ΅¨σ΅¨σ΅¨ππ+1 σ΅¨σ΅¨σ΅¨σ΅¨ 2 (21) πππ΅1 , 2 (πΌπ + 2π½) π§πσΈ (π§) π(π§) πΌ π(π§) πΌ 2 2 ( ) } + {(1 − π½) ( π ) + π½ π π π§ ππ (π§) π§π =1+ 2 1 (πΌπ + π½) ππ+1 π§ + (πΌπ + 2π½) ππ ππ 2 } π§2 + × {2ππ+2 + (πΌ − 1) ππ+1 π΅ (πΌπ + π½) 1 (2 (1 + 2 ) πππ΅1 π΅1 (πΌπ + 2π½) πππ΅1 σ΅¨2 σ΅¨ − (2π + πΌ − 1) ) σ΅¨σ΅¨σ΅¨σ΅¨ππ+1 σ΅¨σ΅¨σ΅¨σ΅¨ 2 + (22) (28) (πΌ − 1) (πΌ − 2) 3 ππ+1 } π§3 + ⋅ ⋅ ⋅ . 6 Also, we have π (π€ (π§)) = 1 + π΅1 π€1 π§ + (π΅1 π€2 + π΅1 π€12 ) π§2 πππ΅1 . 2 (πΌπ + 2π½) + (π΅1 π€3 + 2π΅2 π€1 π€2 + π΅3 π€13 ) π§3 + ⋅ ⋅ ⋅ . (29) Comparing the coefficients of π§, π§2 , π§3 and after simple calculations, we obtain For any complex number π, σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ σ΅¨σ΅¨ πππ΅ πππ΅1 π΅ σ΅¨σ΅¨σ΅¨ σ΅¨ 1 max {1, σ΅¨σ΅¨σ΅¨ Φ (π, πΌ, π½, π) − 2 σ΅¨σ΅¨σ΅¨} . σ΅¨σ΅¨ 2 π΅1 σ΅¨σ΅¨ 2 (πΌπ + 2π½) (23) ππ+1 = πππ΅1 π€1 , 2 (πΌπ + π½) ππ+2 = πππ΅1 2 (πΌπ + 2π½) × {π€2 − ( Also, πππ΅1 σ΅¨σ΅¨ σ΅¨ σ΅¨σ΅¨ππ+3 σ΅¨σ΅¨σ΅¨ ≤ σ΅¨ σ΅¨ 2 (πΌπ + 3π½) π» (π1 , π2 ) , 2 (πΌπ + 3π½) ππ × {ππ+3 + (πΌ − 1) ππ+1 ππ+2 2 ≤ π§πσΈ (π§) π(π§) πΌ π(π§) πΌ 2 2 ) } + {(1 − π½) ( π ) + π½ ( π π π§ ππ (π§) π§π (27) Now, 1− σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ ≤ (26) = π (π€ (π§)) . and for π3 ≤ π ≤ π2 , + π§∈πΈ such that σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ ≤ πππ΅2 (1 − πΌ) (πΌπ + 3π½) . 2 (πΌπ + π½) (πΌπ + 2π½) These results are sharp. Furthermore, for π1 ≤ π ≤ π3 , + (25) ππ+3 = (24) πππ΅1 (πΌ − 1) (πΌπ + 2π½) π΅2 − ) π€12 } , 2 2 π΅1 2(πΌπ + π½) πππ΅1 {π€ + π1 π€1 π€2 + π2 π€13 } , 2 (πΌπ + 2π½) 3 (30) Journal of Applied Mathematics 5 where π1 and π2 are defined in (25). It can be easily followed from (30) that 2 = ππ+2 − πππ+1 πππ΅1 {π€ − ]π€12 } , 2 (πΌπ + 2π½) 2 (31) 2.1. Application of Theorem 6 to the Function Defined by Convolutions where ]= πππ΅1 π΅ Φ (π, πΌ, π½, π) − 2 . 2 π΅1 Corollary 10. For π = 2, π = 1, πΌ = 0, and π½ = 1, the results from (20) to (22) coincide with the results obtained by Ma and Minda [2] for the class π∗ (π). (32) The results from (20) to (22) are obtained by using Lemma 3, (23) by using Lemma 4, and (24) by using Lemma 5. To show that these results are sharp, we define the functions πΎππ (π§), πΉπ (π§), and πΊπ (π§) such that Theorem 11. Let π(π§) = 1 + π΅1 π§ + π΅2 π§2 + π΅3 π§3 + ⋅ ⋅ ⋅ , where π΅π , π are real with π΅1 > 0 and π΅2 ≥ 0. Let π1 = σΈ πΊπ (0) = πΊπσΈ (33) − πππ΅12 (0) − 1 = 0, with σΈ π§πΎππ (π§) πΎππ (π§) πΌ πΎππ (π§) πΌ 2 2 ( π ) } 1 − + {(1 − π½) ( π ) + π½ π π π§ ππΎππ (π§) π§ π2 = π§ (π§ + π) ). 1 + ππ§ π3 = It is clear that the functions πΎππ , πΉπ , πΊπ ∈ ππ,π,πΌ,π½ (π). Let πΎπ : = πΎπ2 . If π < π1 or π > π2 , then the equality occurs for the function πΎπ or one of its rotations. For π1 < π < π2 , the equality is attained, if and only if π is πΎπ3 or one of its rotations. When π = π1 , then the equality holds for the function πΉπ or one of its rotations. If π = π2 , then the equality is obtained for the function πΊπ or one of its rotations. Corollary 7. For π = 2, the results from (20) to (24) coincide with the results proved by Ramachandran et al. [8]. Corollary 8. For π = 2, π = 1, and π½ = 1, the results from (20) to (22) coincide with the results obtained by Ravichandran et al. [4] for the class π΅πΌ (π). Corollary 9. For π = 2, πΌ = 0, and π½ = 1, the results from (20) to (24) coincide with the results obtained by Ali et al. [1] for the class ππ∗ (π). }, 2 (πΌ − 1) (πΌπ + 2π½) 2 ππ+1 Φ∗ (π, πΌ, π½, π) = 2(πΌπ + π½) 2 }, 2 (πΌπ + π½) ππ+2 πππ΅12 (πΌπ + 2π½) × {2π΅2 − πππ΅12 (34) 2 (πΌπ + π½) ππ+2 πππ΅12 (πΌπ + 2π½) − πππ΅12 π§πΊσΈ (π§) πΊπ (π§) πΌ πΊ (π§) πΌ 2 2 ( π ) } + {(1 − π½) ( π π ) + π½ π π π π§ ππΊπ (π§) π§ βΊ π (− 2(πΌπ + π½) 2 ππ+1 π§πΉσΈ (π§) πΉπ (π§) πΌ πΉ (π§) πΌ 2 2 1 − + {(1 − π½) ( π π ) + π½ π ) } ( π π π§ ππΉπ (π§) π§π π§ (π§ + π) βΊ π( ), 1 + ππ§ (πΌ − 1) (πΌπ + 2π½) × {2 (π΅2 + π΅1 ) βΊ π (π§π−1 ) , 1− 2 (πΌπ + π½) ππ+2 πππ΅12 (πΌπ + 2π½) × {2 (π΅2 − π΅1 ) πΎππ (0) = [πΎππ ] (0) − 1 = 0, πΉπ (0) = πΉπσΈ (0) − 1 = 0, 2 ππ+1 (πΌ − 1) (πΌπ + 2π½) 2 2(πΌπ + π½) }, (πΌπ + 2π½) (2π (ππ+2 /ππ+1 ) + πΌ − 1) 2 2(πΌπ + π½) . (35) If π(π§) is of the form (1) and belongs to the class ππ,π,πΌ,π½,π (π), then σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨ σ΅¨ πππ΅12 ∗ ππ { { − (π΅ Φ (π, πΌ, π½, π)) , { 2 { 2 { { 2ππ+2 (πΌπ + 2π½) { { { π < π1 , { { { { πππ΅1 { π1 ≤ π ≤ π2 , ≤ { 2π (πΌπ + 2π½) , { π+2 { { { { πππ΅12 ∗ ππ { { { ( Φ (π, πΌ, π½, π) − π΅2 ) , { { 2 2ππ+2 (πΌπ + 2π½) { { { π > π2 . { (36) 6 Journal of Applied Mathematics Furthermore, for π1 ≤ π ≤ π3 , Proof. Since π ∈ ππ,π,πΌ,π½,π (π), therefore we have for a Schwarz function π€, such that σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ + πΌ 2 ππ+1 2 πππ΅1 ππ+2 (2 (1 − + ≤ 1− π΅2 (πΌπ + π½) ) π΅1 (πΌπ + 2π½) (π ∗ π) (π§) 2 2 ) + { (1 − π½) ( π π π§π σΈ +π½ ππ+2 πππ΅1 σ΅¨2 σ΅¨ + πΌ − 1) ) σ΅¨σ΅¨σ΅¨σ΅¨ππ+1 σ΅¨σ΅¨σ΅¨σ΅¨ (2π 2 ππ+1 πππ΅1 , 2ππ+2 (πΌπ + 2π½) Now, πΌ (37) 1− (π ∗ π) (π§) 2 2 ) + { (1 − π½) ( π π π§π and for π3 ≤ π ≤ π2 , σΈ +π½ σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ + 2 ππ+1 πππ΅1 ππ+2 =1+ 2 π΅ (πΌπ + π½) (2 (1 + 2 ) π΅1 (πΌπ + 2π½) − ≤ πΌ π§(π ∗ π) (π§) (π ∗ π) (π§) ( ) } = π (π€ (π§)) . π§π π (π ∗ π) (π§) (42) ππ+2 πππ΅1 σ΅¨2 σ΅¨ + πΌ − 1) ) σ΅¨σ΅¨σ΅¨σ΅¨ππ+1 σ΅¨σ΅¨σ΅¨σ΅¨ (2π 2 ππ+1 πππ΅1 . 2ππ+2 (πΌπ + 2π½) πΌ π§(π ∗ π) (π§) (π ∗ π) (π§) ) } ( π§π π (π ∗ π) (π§) 2 1 (πΌπ + π½) ππ+1 ππ+1 π§ + (πΌπ + 2π½) ππ ππ 2 2 ππ+1 } π§2 + × {2ππ+2 ππ+2 + (πΌ − 1) ππ+1 2 (πΌπ + 3π½) ππ {ππ+3 ππ+3 + (πΌ − 1) ππ+1 ππ+2 ππ+1 ππ+2 } 3 ×{ (πΌ − 1) (πΌ − 2) 3 3 }π§ + ⋅⋅⋅ . + ππ+1 ππ+1 6 } { (43) (38) Also, we obtain For any complex number π, π (π€ (π§)) = 1 + π΅1 π€1 π§ + (π΅1 π€2 + π΅1 π€12 ) π§2 σ΅¨σ΅¨ 2 σ΅¨σ΅¨ σ΅¨σ΅¨ππ+2 − πππ+1 σ΅¨σ΅¨ σ΅¨ σ΅¨ ≤ σ΅¨σ΅¨ πππ΅ πππ΅1 π΅ σ΅¨σ΅¨σ΅¨ σ΅¨ 1 ∗ max {1, σ΅¨σ΅¨σ΅¨ Φ (π, πΌ, π½, π) − 2 σ΅¨σ΅¨σ΅¨} . σ΅¨σ΅¨ 2 π΅1 σ΅¨σ΅¨ 2ππ+2 (πΌπ + 2π½) (39) Also, πππ΅1 σ΅¨σ΅¨ σ΅¨ σ΅¨σ΅¨ππ+3 σ΅¨σ΅¨σ΅¨ ≤ σ΅¨ σ΅¨ 2 (πΌπ + 3π½) π π» (π1 , π2 ) , π+3 (40) + (π΅1 π€3 + 2π΅2 π€1 π€2 + π΅3 π€13 ) π§3 + ⋅ ⋅ ⋅ . Comparing the coefficients of π§, π§2 , π§3 and after simple calculations, we obtain ππ+1 = πππ΅1 π€1 , 2ππ+1 (πΌπ + π½) ππ+2 = πππ΅1 2ππ+2 (πΌπ + 2π½) where π»(π1 , π2 ) is defined in Lemma 5 and π1 = 2π΅2 πππ΅1 (1 − πΌ) (πΌπ + 3π½) + , π΅1 2 (πΌπ + π½) (πΌπ + 2π½) π2 = πππ΅1 2 (πΌ − 1) (2πΌ − 1) (πΌπ + 3π½) π΅3 +( ) 3 π΅1 2 6(πΌπ + π½) + πππ΅2 (1 − πΌ) (πΌπ + 3π½) . 2 (πΌπ + π½) (πΌπ + 2π½) These results are sharp. (44) × {π€2 − ( ππ+3 = πππ΅1 (πΌ − 1) (πΌπ + 2π½) π΅2 − ) π€12 } , 2 2 π΅1 2(πΌπ + π½) πππ΅1 {π€ + π1 π€1 π€2 + π2 π€13 } . 2ππ+3 (πΌπ + 2π½) 3 (45) (41) The remaining proof of the theorem is similar to the proof of Theorem 6. Corollary 12. For π = 2, the results from (36) to (40) coincide with the results proved by Ramachandran et al. [8] for the class π π,1,πΌ,π½,π (π). Journal of Applied Mathematics 7 Corollary 13. For π = 2, πΌ = 0, and π½ = 1, the results from (36) to (40) coincide with the results obtained by Ali et al. [1] ∗ (π). for the class ππ,π Corollary 14. For π = 2, π = 1, πΌ = 0, and π½ = 1, π2 = 2 Γ (3) Γ (2 − π) = , Γ (3 − π) 2−π π3 = Γ (4) Γ (2 − π) 6 , = − π) Γ (4 − π) (2 (3 − π) π΅1 = 8 , π2 π΅2 = (46) 16 , 3π2 the results from (36) to (38) coincide with the results obtained by Srivastava and Mishra [9]. Acknowledgment The work here is fully supported by LRGS/TD/2011/UKM/ ICT/03/02. References [1] R. M. Ali, V. Ravichandran, and N. Seenivasagan, “Coefficient bounds for π-valent functions,” Applied Mathematics and Computation, vol. 187, no. 1, pp. 35–46, 2007. [2] W. C. Ma and D. Minda, “A unified treatment of some special classes of univalent functions,” in Proceedings of the Conference on Complex Analysis, pp. 157–169, International Press, 1994. [3] S. Owa, “Properties of certain integral operators,” Southeast Asian Bulletin of Mathematics, vol. 24, no. 3, pp. 411–419, 2000. [4] V. Ravichandran, A. Gangadharan, and M. Darus, “FeketeSzegoΜ inequality for certain class of Bazilevic functions,” Far East Journal of Mathematical Sciences, vol. 15, no. 2, pp. 171–180, 2004. [5] M. P. Chen, “On the regular functions satisfying π π{π(π§)/π§} > π,” Bulletin of the Institute of Mathematics. Academia Sinica, vol. 3, no. 1, pp. 65–70, 1975. [6] F. R. Keogh and E. P. Merkes, “A coefficient inequality for certain classes of analytic functions,” Proceedings of the American Mathematical Society, vol. 20, pp. 8–12, 1969. [7] D. V. Prokhorov and J. Szynal, “Inverse coefficients for (πΌ, π½)-convex functions,” Annales Universitatis Mariae CurieSkΕodowska A, vol. 35, pp. 125–143, 1981. [8] C. Ramachandran, S. Sivasubramanian, and H. Silverman, “Certain coefficient bounds for π-valent functions,” International Journal of Mathematics and Mathematical Sciences, vol. 2007, Article ID 46576, 11 pages, 2007. [9] H. M. Srivastava and A. K. Mishra, “Applications of fractional calculus to parabolic starlike and uniformly convex functions,” Computers & Mathematics with Applications, vol. 39, no. 3-4, pp. 57–69, 2000. 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