Math Problem Statement

(2 + 7i)(5 - 9i)

Solution

The problem involves multiplying two complex numbers: (2+7i)(2 + 7i) and (59i)(5 - 9i). The goal is to simplify the expression in the form a+bia + bi, where aa and bb are real numbers.

Let's solve it step-by-step using the distributive property (also known as FOIL method for binomials):

(2+7i)(59i)=2(5)+2(9i)+7i(5)+7i(9i)(2 + 7i)(5 - 9i) = 2(5) + 2(-9i) + 7i(5) + 7i(-9i)

  1. 2(5)=102(5) = 10
  2. 2(9i)=18i2(-9i) = -18i
  3. 7i(5)=35i7i(5) = 35i
  4. 7i(9i)=63i27i(-9i) = -63i^2

Since i2=1i^2 = -1, the last term becomes:

63i2=63(1)=63-63i^2 = -63(-1) = 63

Now, add all the terms together:

10+(18i)+35i+6310 + (-18i) + 35i + 63

Combine like terms:

  1. Real part: 10+63=7310 + 63 = 73
  2. Imaginary part: 18i+35i=17i-18i + 35i = 17i

So, the result is:

73+17i73 + 17i

Thus, the simplified answer is 73+17i73 + 17i.

Would you like further details or have any questions? Here are five related questions:

  1. How do you multiply complex numbers using the FOIL method?
  2. Why does i2=1i^2 = -1?
  3. Can you explain why the real and imaginary parts are combined separately?
  4. How would you divide complex numbers?
  5. What happens if both complex numbers have negative real parts?

Tip: Always remember to use i2=1i^2 = -1 when simplifying complex number multiplications!

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Multiplication of Complex Numbers

Formulas

(a + bi)(c + di) = ac + adi + bci + bdi^2
i^2 = -1

Theorems

Properties of Complex Numbers
FOIL Method for Binomials

Suitable Grade Level

High School (Grades 9-12)