Objectives: 1. To simplify powers of complex numbers 2. To add, subtract, multiply, and divide complex numbers 3. To find complex solutions to quadratic equations • • • • • • Assignment: P. 167: 17-26 (Some) P. 167: 27-36 (Some) P. 167: 45-54 (Some) P. 168: 65-74 (Some) P. 168: 86 Binomial Theorem Presentation and Supplement Explain the humor (if any) in this sassy t-shirt. Which of the following do not belong? A. x2 – 1 = 0 B. x2 + 1 = 0 C. −x2 + 1 = 0 D. −(x2 – 1) = 0 Find a number that does not fit into any nook or cranny of the Venn Diagram below. Real Number Complex Number Imaginary Unit Imaginary Number Pure Imaginary Number Complex Plane Complex Conjugates You will be able to simplify powers of complex numbers Graph y = x2 + 1. What are the xintercepts? Solve the quadratic equation x2 + 1 = 0. The problem here is that −1 is not a real number since there is no real number that you can square to get −1. – This does not mean there is no solution; it’s more complex than that. The imaginary unit i can be used to find the square roots of negative numbers. 𝑖 = −1 𝑖 2 = −1 A pattern exists as a result of raising i, an imaginary number, to n, an integer greater than or equal to 1. According to the table, what is the value of i raised to the 16th power? in Solution i1 −1 −1 i2 i3 i4 i5 i6 − −1 1 −1 −1 As the previous example shows, there are only 4 possible values for in. i1 1 i 2 2 i 1 1 All other powers of 4 just repeat this pattern. i 3 i 2 i 1 i i i 4 i 2 i 2 1 1 1 So, how do you think you would evaluate i101? As the previous example shows, there are only 4 possible values for in. i1 1 i 2 2 i 1 1 i i i 1 i i i 4 i 2 i 2 1 1 1 3 2 Divide the exponent by 4, then use the remainder to find the result: Remainder Result 1 i 2 −1 3 −i 0 1 Evaluate each of the following. 1. i54 2. i120 3. i89 4. i39 How can you tell if a number is divisible by 4? Any multiple of 100 is divisible by 4. Note that 100𝑛 is multiple of 4, where 𝑛 ∈ ℤ 100𝑛 100 = 𝑛 = 25𝑛 4 4 Since this is an integer with no remainder, any multiple of 100 is divisible by 4. How can you tell if a number is divisible by 4? If the last two digits of a number are divisible by 4, the whole number is divisible by 4. 132 100 + 32 100 32 = = + = 25 + 8 = 33 4 4 4 4 Since this is an integer with no remainder, as long as the last two digits are divisible by 4, the whole number is divisible by 4. How can you tell if a number is divisible by 4? If the last two digits of a number are divisible by 4, the whole number is divisible by 4. 228 200 + 28 200 28 = = + = 50 + 7 = 57 4 4 4 4 Since this is an integer with no remainder, as long as the last two digits are divisible by 4, the whole number is divisible by 4. How can you tell if a number is divisible by 4? If the last two digits of a number are divisible by 4, the whole number is divisible by 4. 316 300 + 16 300 16 = = + = 75 + 4 = 79 4 4 4 4 Since this is an integer with no remainder, as long as the last two digits are divisible by 4, the whole number is divisible by 4. Simplify each of the following. 1. −36 2. −13 3. 𝑖 5 2 The Square Root of a Negative Number Property Example 1. If r is a positive number, then −𝑟 = 𝑖 𝑟 −5 = 𝑖 5 2 2. 𝑖 𝑟 2 = −𝑟 𝑖 5 = 𝑖2 ∙ 5 = −5 Find the roots of each quadratic equation. 1. x2 + 11 = 3 2. 2x2 + 18 = -72 A complex number in standard form is written a bi Real Part 𝑎, 𝑏 ∈ ℝ Imaginary Part • All real numbers are complex numbers – This happens when b = 0 • For imaginary numbers, b 0. • For a pure imaginary number, a = 0. Draw a Venn Diagram that represents the set of complex numbers and includes real, imaginary, and pure imaginary numbers. ℂ: The set of all complex numbers All complex numbers are essentially 2-dimensional. – When you graph a real number, it appears on a 1-D number line All complex numbers are essentially 2-dimensional. – However, complex numbers have both a real and an imaginary part. Imaginary Axis Real Axis You will be able to add, subtract, multiply, and divide complex numbers To add or subtract two complex numbers, simply add or subtract their real and imaginary parts separately. Sum (a + bi) + (c + di) = (a + c) + (b + d)i Difference (a + bi) – (c + di) = (a – c) + (b – d)i Write the expression as a complex number in standard form. 1. (12 – 11i) + (−8 + 3i) 2. (15 – 9i) – (24 – 9i) 3. 35 – (13 + 4i) + i Write the expression as a complex number in standard form. 1. (9 – i) + (−6 + 7i) 2. (3 + 7i) – (8 – 2i) 3. −4 – (1 + i) – (5 + 9i) To multiply complex numbers, you have to use a combination of the distributive property and properties of the imaginary unit. 2i 3 5i 6i 10i 2 6i 10 1 6i 10 10 6i Write the expression as a complex number in standard from. 1. −5i(8 – 9i) 2. (−8 + 2i)(4 – 7i) Write the expression as a complex number in standard from. 1. i(9 – i) 2. (3 + i)(5 – i) Multiply and classify the product. 1. (5i)(−5i) 2. (3 + 6i)(3 – 6i) To “divide” complex numbers, you have to multiply by a complex conjugate The complex numbers a + bi and a – bi are complex conjugates The product of complex conjugates is always a real number 2 3i 1 i 2 3i 1 i 2 2i 3i 3i 2 1 5i 1 i 1 i 2 2 1 i 1 i To “divide” complex numbers, you have to multiply by a complex conjugate The complex numbers a + bi and a – bi are complex conjugates The product of complex conjugates is always a real number 2 3i 1 i 2 3i 1 i 2 2i 3i 3i 2 1 5 i 1 i 1 i 2 2 2 1 i 1 i Write the quotient in standard form. 3 4i 5i Write each quotient in standard form. 5 1. 1 i 5 2i 2. 3 2i Evaluate each of the following. 1. i−5 2. i−12 3. i−31 4. i−102 Simplify each of the following: 1. 1 + 𝑖 3 2. 1 + 𝑖 −3 You will be able to find complex solutions to quadratic equations Solve each quadratic equation. 2 1. x 6 x 12 0 2. 2 x 4 x 14 0 2 Objectives: 1. To simplify powers of complex numbers 2. To add, subtract, multiply, and divide complex numbers 3. To find complex solutions to quadratic equations • • • • • • Assignment: P. 167: 17-26 (Some) P. 167: 27-36 (Some) P. 167: 45-54 (Some) P. 168: 65-74 (Some) P. 168: 86 Binomial Theorem Presentation and Supplement