Hindawi Publishing Corporation Discrete Dynamics in Nature and Society Volume 2011, Article ID 932362, 12 pages doi:10.1155/2011/932362 Research Article On the Behavior of Solutions of the System of Rational Difference Equations: xn1 xn−1 /yn xn−1 − 1, yn1 yn−1 /xn yn−1 − 1, and zn1 zn−1 /yn zn−1 − 1 Abdullah Selçuk Kurbanli Department of Mathematics, Faculty of Education, Selcuk University, 42090 Konya, Turkey Correspondence should be addressed to Abdullah Selçuk Kurbanli, agurban@selcuk.edu.tr Received 23 December 2010; Accepted 26 January 2011 Academic Editor: Ibrahim Yalcinkaya Copyright q 2011 Abdullah Selçuk Kurbanli. 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. We investigate the solutions of the system of difference equations xn1 xn−1 /yn xn−1 − 1, yn1 yn−1 /xn yn−1 − 1, zn1 zn−1 /yn zn−1 − 1, where y0 , y−1 , x0 , x−1 , z−1 , z0 ∈ R. 1. Introduction Recently, there has been great interest in studying difference equation systems. One of the reasons for this is a necessity for some techniques which can be used in investigating equations arising in mathematical models describing real life situations in population biology, economic, probability theory, genetics, psychology, and so forth. There are many papers related to the difference equations system, for example, the following papers. In 1, Çinar studied the solutions of the systems of the difference equations xn1 1 , yn yn1 yn . xn−1 yn−1 1.1 In 2 Papaschinopoulos and Schinas studied the oscillatory behavior, the boundedness of the solutions, and the global asymptotic stability of the positive equilibrium of the system of nonlinear difference equations xn1 A yn , xn−p yn1 A xn , yn−q n 0, 1, . . . , p, q. 1.2 2 Discrete Dynamics in Nature and Society In 3 Papaschinopoulos and Schinas proved the boundedness, persistence, the oscillatory behavior, and the asymptotic behavior of the positive solutions of the system of difference equations k Ai xn1 yn1 pi , i0 yn−i k Bi q i xn−i i0 1.3 . In 4, 5 Özban studied the positive solutions of the system of rational difference equations xn xn1 a yn−3 1 yn−k yn , , yn1 byn−3 , xn−q yn−q 1.4 yn . xn−m yn−m−k In 6, 7 Clark and Kulenović investigate the global asymptotic stability xn1 xn , a cyn yn1 yn . b dxn 1.5 In 8 Camouzis and Papaschinopoulos studied the global asymptotic behavior of positive solutions of the system of rational difference equations xn1 1 xn , yn−m yn1 1 yn . xn−m 1.6 In 9 Yang et al. considered the behavior of the positive solutions of the system of the difference equations xn a yn−p , yn byn−p . xn−q yn−q 1.7 In 10 Kulenović and Nurkanović studied the global asymptotic behavior of solutions of the system of difference equations xn1 a xn , b yn yn1 c yn , d zn zn1 e zn . f xn 1.8 In 11 Zhang et al. investigated the behavior of the positive solutions of the system of difference equations xn A 1 , yn−p yn A yn−1 . xn−r yn−s 1.9 Discrete Dynamics in Nature and Society 3 In 12 Zhang et al. studied the boundedness, the persistence, and global asymptotic stability of the positive solutions of the system of difference equations xn1 A yn−m , xn yn1 A xn−m . yn 1.10 In 13 Yalcinkaya studied the global asymptotic behavior of a system of two nonlinear difference equations. In 14 Yalcinkaya et al. investigated the solutions of the system of difference equations 2 xn 1 xn1 3 xn 2 2 xn − 1 , xn1 1 xn k 3 xn − 1 , . . . , xn1 1 xn − 1 1.11 . In 15 Yalcinkaya studied the global asymptotic stability of the system of difference equations zn1 tn zn−1 a , tn zn−1 zn tn−1 a . zn tn−1 tn1 1.12 In 16 Irićanin and Stević studied the positive solutions of the system of difference equations 2 1 xn1 1 xn1 1 2 xn 1 xn 3 xn−1 3 xn−1 4 xn−2 2 , xn1 2 , xn1 1 3 1 xn 4 xn−1 3 xn 5 xn−2 1 k , . . . , xn1 4 xn−1 1 xn 2 xn−1 k , . . . , xn1 1 , 1 xn 2 xn−1 3 xn−2 1.13 . In 17 Kurbanli et al. studied the behavaior of positive solutions of the system of rational difference equations xn1 xn−1 , yn xn−1 1 yn1 yn−1 . xn yn−1 1 1.14 Also see references. In this paper, we investigate the behavior of the solutions of the difference equations system xn1 xn−1 , yn xn−1 − 1 yn1 yn−1 , xn yn−1 − 1 where the initial conditions are arbitrary real numbers. zn1 zn−1 , yn zn−1 − 1 1.15 4 Discrete Dynamics in Nature and Society Theorem 1.1. Let y0 , y−1 , x0 , x−1 , z−1 , z0 ∈ R be arbitrary real numbers and y0 a, y−1 b, x0 c, x−1 d, z0 e, z−1 f and let {xn , yn , zn } be a solution of the system 1.15. Also, assume that af / 1 and bc / 1 then all solutions of 1.15 are ⎧ ⎪ ⎨ d n-odd, n, xn ad − 1 ⎪ ⎩cbc − 1n , n-even, ⎧ b ⎪ ⎨ n-odd, n, yn bc − 1 ⎪ ⎩aad − 1n , n-even, zn ⎧ f ⎪ ⎪ ⎪ n n n n , ⎪ ⎪ 0 1 n n−1 n−1 n−2 ⎪ −1 0 a fd −1 1 a fd · · · −1n−1 n−1 a1 fd0 −1n n ⎪ ⎪ ⎪ ⎪ ⎪ ⎨ n-odd ⎪ bc − 1n e ⎪ ⎪ , n n n n ⎪ −1n ⎪ ⎪ n 1 c0 e · · · −11 n cn−1 e −10 n cn · · · −1n 0 c0 ⎪ b b b b −1 ⎪ ⎪ n n 0 1 ⎪ ⎪ ⎩ n-even. 1.16 Proof. For n 0, 1, 2, 3, we have x2 y2 z2 z3 d x−1 , y0 x−1 − 1 ad − 1 y1 y−1 b , x0 y−1 − 1 bc − 1 z1 f z−1 , y0 z−1 − 1 af − 1 c x0 cbc − 1 cbc − 1, y1 x0 − 1 b/bc − 1c − 1 bc − bc 1 y0 a aad − 1 aad − 1, x1 y0 − 1 d/ad − 1a − 1 ad − ad 1 e ebc − 1 ebc − 1 z0 − , y1 z0 − 1 b/bc − 1e − 1 be − bc 1 −1 · be bc − 1 x3 y3 x1 d/ad − 1 d x1 , y2 x1 − 1 aad − 1 · d/ad − 1 − 1 ad − 12 y1 b/bc − 1 x2 y1 − 1 cbc − 1 · b/bc − 1 − 1 b/bc − 1 b , bc − 1 bc − 12 f/ af − 1 f/ af − 1 f z1 2 2 y2 z1 − 1 aad − 1 · f/ af − 1 − 1 a df − 2af 1 a df − af − af 1 / af − 1 1.17 Discrete Dynamics in Nature and Society 5 for n k assume that xk yk z2k−1 −1 0 k 0 ak fdk−1 −1 1 ⎧ ⎪ ⎪ ⎨ ⎪ ⎪ ⎩ ⎧ ⎪ ⎪ ⎨ ⎪ ⎪ ⎩ d , ad − 1k k-odd, cbc − 1k , b bc − 1k k-even, , k-odd, aad − 1k , f k 1 k-even, ak−1 fdk−2 · · · −1k−1 k k−1 a1 fd0 −1k k , k k 1, 2, . . . , z2k −1k −1k k 1 b1 c0 e · · · −11 bc − 1k e k bk ck−1 e −10 k k k 0 k bk ck · · · −1k b1 c1 , k 1, 2, . . . 1.18 are true. Then for n k 1 we will show that 1.16 is true. From 1.15, we have x2k1 d/ad − 1k x2k−1 d . y2k x2k−1 − 1 aad − 1k · d/ad − 1k − 1 ad − 1k1 1.19 Also, similarly from 1.15, we have y2k1 y2k−1 b/bc − 1k b , x2k y2k−1 − 1 cbc − 1k · b/bc − 1k − 1 bc − 1k1 n k n! , n − k! · k! 1.20 n n k n 0 k−1 n n n1 k n1 n1 , 6 Discrete Dynamics in Nature and Society from properties of Binomial coefficients, z2k1 z2k−1 y2k z2k−1 − 1 k a1 fd0 −1k kk f/ −10 k0 ak fdk−1 · · · −1k−1 k−1 k aad − 1k f/ −10 k0 ak fdk−1 · · · −1k−1 k−1 a1 fd0 −1k kk − 1 f −1 0 k1 0 ak1 fdk −1 1 k1 1 ak fdk−1 · · · −1k k1 k a1 fd0 −1k! k1 k1 1.21 written and accurate. Also, we have x2k2 cbc − 1k x2k cbc − 1k cbc − 1k1 , y2k1 x2k − 1 b/bc − 1k1 cbc − 1k − 1 bc/bc − 1 − 1 y2k2 y2k aad − 1k aad − 1k aad − 1k! , x2k1 y2k − 1 d/ad − 1k1 · aad − 1k − 1 ad/ad − 1 − 1 z2k2 z2k y2k1 z2k − 1 −1k bc − 1k e/ A −10 k0 bk ck · · · −1k kk b0 c0 −1k1 k1 k k 0 k k k k k 0 0 b/bc − 1 · −1 bc − 1 e/ A −1 0 b c · · · −1 k b c − 1 × bc − 1k1 e −1k1 k1 1 b1 c0 e· · ·−11 where A denotes −1k k 1 k1 k1 bk1 ck e −10 b1 c0 e · · · −11 k k k1 0 bk1 ck1 · · ·−1k1 k1 k1 , b1 c1 1.22 bk ck−1 e. Corollary 1.2. Let a, b, c, d be only positive real numbers or negative real numbers and let e, f be arbitrary nonnegative real numbers, and let {xn , yn , zn } be a solution of the system 1.15. If ad / 1, bc / 1, 0 < ad < 1 and 0 < bc < 1 then one has lim x2n−1 lim y2n−1 ∞, n→∞ n→∞ 1.23 lim x2n lim y2n 0. n→∞ n→∞ Discrete Dynamics in Nature and Society 7 Proof. From ad / 1, bc / 1, 0 < ad < 1 and 0 < bc < 1 we have −1 < ad − 1 < 0 and −1 < bc − 1 < 0. Hence, we have x2n−1 d , ad − 1n y2n−1 x2n cbc − 1n , b , bc − 1n 1.24 y2n aad − 1n . Then, lim x2n−1 lim n→∞ n → ∞ ad lim y2n−1 lim n→∞ n → ∞ bc ⎧ ⎪ ∞, d > 0, n-even ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨∞, d < 0, n-odd d − 1n ⎪ ⎪ −∞, d > 0, n-odd ⎪ ⎪ ⎪ ⎪ ⎪ ⎩−∞, d < 0, n-even, ⎧ ⎪ ⎪ ⎪∞, b > 0, n-even ⎪ ⎪ ⎪ ⎪ ⎨∞, b < 0, n-odd 1.25 b − 1n ⎪ ⎪ −∞, b > 0, n-odd ⎪ ⎪ ⎪ ⎪ ⎪ ⎩ −∞, b < 0, n-even. Also, lim x2n lim cbc − 1n 0, n→∞ n→∞ 1.26 n lim y2n lim aad − 1 0. n→∞ n→∞ Example 1.3. If y0 −1/2, y−1 −1/2, x0 −1/2, x−1 −1/2, then the solutions of 1.15 can be represented by Table 1. Corollary 1.4. Let a, b, c, d be only positive real numbers or negative real numbers and let e, f be arbitrary nonnegative real numbers, and let {xn , yn , zn } be a solution of the system 1.15. If ad / 1, bc / 1, 1 < ad < 2 and 1 < bc < 2 then one has lim x2n−1 lim y2n−1 ∞, n→∞ n→∞ lim x2n lim y2n 0. n→∞ n→∞ 1.27 8 Discrete Dynamics in Nature and Society Table 1 i 1 2 3 4 5 6 7 8 x2i−1 0.6667 −0.8889 1.1852 −1.5803 2.1070 −2.8093 3.7458 −4.9944 x2i 0.3750 −0.2813 0.2109 −0.1582 0.1187 −0.0890 0.0667 −0.0501 y2i−1 0.6667 −0.8889 1.1852 −1.5803 2.1070 −2.8093 3.7458 −4.9944 y2i 0.3750 −0.2813 0.2109 −0.1582 0.1187 −0.0890 0.0667 −0.0501 z2i−1 0.6667 −0.8889 1.1852 −1.5803 2.1070 −2.8093 3.7458 −4.9944 z2i 0.3750 −0.2813 0.2109 −0.1582 0.1187 −0.0890 0.0667 −0.0501 Proof. From ad / 1, bc / 1, 1 < ad < 2 and 1 < bc < 2 we have 0 < ad − 1 < 1 and 0 < bc − 1 < 1. Hence, we have x2n−1 d , ad − 1n x2n cbc − 1n , y2n−1 b , bc − 1n 1.28 y2n aad − 1n . Then, lim x2n−1 n→∞ ⎧ ⎨∞, d > 0 d lim n → ∞ ad − 1n ⎩ −∞, d < 0, ⎧ ⎨∞, b > 0 1.29 b n → ∞ bc − 1n ⎩ −∞, b < 0. lim y2n−1 lim n→∞ Also, lim x2n lim cbc − 1n 0, n→∞ n→∞ 1.30 n lim y2n lim aad − 1 0. n→∞ n→∞ Example 1.5. If y0 3/2, y−1 3/4, x0 3/2, x−1 3/4, z0 3/2, z−1 3/4 then the solutions of 1.15 can be represented by Table 2. Corollary 1.6. Let a, b, c, d be only positive real numbers or negative real numbers and let e, f be arbitrary nonnegative real numbers, and let {xn , yn , zn } be a solution of the system 1.15. Discrete Dynamics in Nature and Society 9 If −∞ < ad < 0 and −∞ < bc < 0 then one has lim x2n−1 lim y2n−1 0, n→∞ n→∞ 1.31 lim x2n lim y2n ∞. n→∞ n→∞ Proof. From −∞ < ad < 0 and −∞ < bc < 0 we have −∞ < ad − 1 < −1 and −∞ < bc − 1 < −1. Hence, we have x2n−1 d , ad − 1n x2n cbc − 1n , y2n−1 b , bc − 1n 1.32 y2n aad − 1n . Then, lim x2n−1 lim n→∞ n → ∞ ad d 0, − 1n 1.33 lim y2n−1 lim n→∞ n → ∞ bc b 0. − 1n Also, lim x2n lim cbc − 1n n→∞ n→∞ lim y2n lim aad − 1n n→∞ n→∞ ⎧ ∞, c > 0, n-even ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨∞, c < 0, n-odd ⎪ ⎪ ⎪ −∞, c > 0, n-odd ⎪ ⎪ ⎪ ⎪ ⎪ ⎩ −∞, c < 0, n-even, ⎧ ∞, a > 0, n-even ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎪ ⎨∞, a < 0, n-odd 1.34 ⎪ ⎪ ⎪ −∞, a > 0, n-odd ⎪ ⎪ ⎪ ⎪ ⎪ ⎩ −∞, a < 0, n-even. Example 1.7. If y0 −3/2, y−1 −3/4, x0 3/2, x−1 3/4, z0 3/2, z−1 3/4 then the solutions of 1.15 can be represented by Table 3. 10 Discrete Dynamics in Nature and Society Table 2 i x2i−1 x2i y2i−1 y2i z2i−1 z2i 1 6 0.188 6 0.188 6 0.188 2 48 0.023 48 0.023 48 0.023 3 384 0.003 384 0.003 384 0.003 4 3072 0.0004 3072 0.0004 3072 0.0004 5 24576 0.00004 24576 0.00004 24576 0.00004 6 1.967·105 0.00001 1.967·105 0.00001 1.967·105 0.00001 7 1.573 · 106 7.153 · 10−7 1.573 · 106 7.153 · 10−7 1.573 · 106 7.153 · 10−7 8 1.258 · 107 8.941 · 10−8 1.258 · 107 8.941 · 10−8 1.258 · 107 8.941 · 10−8 Table 3 i x2i−1 x2i y2i−1 y2i z2i−1 z2i 1 −0.3529 −3.1875 0.3529 3.1875 −0.3529 −3.1875 2 0.1661 6.7734 −0.1661 −6.7734 0.1661 6.7734 3 −0.0782 −14.3936 0.0782 14.3936 −0.0782 −14.3936 4 0.0368 30.5863 −0.0368 −30.5863 0.0368 30.5863 5 −0.0173 −64.9959 0.0173 64.9959 −0.0173 −64.9959 6 0.0081 138.1163 −0.0081 −138.1163 0.0081 138.1163 7 −0.0038 −293.4971 0.0038 293.4971 −0.0038 −293.4971 8 0.0018 623.6813 −0.0018 −623.6813 0.0018 623.6813 Corollary 1.8. Let a, b, c, d be only positive real numbers or negative real numbers and let e, f be arbitrary nonnegative real numbers, and let {xn , yn , zn } be a solution of the system 1.15. If 2 < ad < ∞ and 2 < bc < ∞ then one has lim x2n−1 lim y2n−1 0, n→∞ n→∞ 1.35 lim x2n lim y2n ∞. n→∞ n→∞ Proof. From 2 < ad < ∞ and 2 < bc < ∞ we have 1 < ad − 1 < ∞ and 1 < bc − 1 < ∞. Hence, we have x2n−1 d , ad − 1n x2n cbc − 1n , y2n−1 b , bc − 1n 1.36 y2n aad − 1n . Then, lim x2n−1 lim n→∞ n → ∞ ad d 0, − 1n 1.37 lim y2n−1 lim n→∞ n → ∞ bc b 0. − 1n Discrete Dynamics in Nature and Society 11 Table 4 i x2i−1 x2i y2i−1 y2i z2i−1 z2i 1 0.546 4.125 0.909 6.875 0.546 4.125 2 0.198 11.344 0.331 18.906 0.198 11.344 3 0.072 31.195 0.120 51.992 0.072 31.195 4 0.026 85.787 0.044 142.979 0.026 85.787 5 0.010 235.915 0.016 393.191 0.010 235.915 6 0.004 648.765 0.006 1081.275 0.004 648.765 7 0.001 1784.104 0.002 2973.506 0.001 1784.104 8 0.0005 4906.285 0.001 8177.142 0.0005 4906.285 Also, lim x2n lim cbc − 1n n→∞ n→∞ lim y2n lim aad − 1n n→∞ n→∞ ⎧ ⎨∞, c > 0 ⎩−∞, c < 0, ⎧ ⎨∞, a > 0 1.38 ⎩−∞, a < 0. Example 1.9. If y0 5/2, y−1 5/2, x0 3/2, x−1 3/2, z0 3/2, z−1 3/2 then the solutions of 1.15 can be represented by Table 4. Acknowledgment The authors are grateful to the anonymous referees for their valuable suggestions that improved the quality of this study. References 1 C. 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