Math Problem Statement

(7 + 5i)(8 - 9i) = ? (Simplify and express in the form a + bi)

Solution

The problem is asking you to multiply two complex numbers: (7+5i)(7 + 5i) and (89i)(8 - 9i), and express the result in the form a+bia + bi.

Let's go through the steps:

  1. Multiply the two binomials using the distributive property (FOIL method): (7+5i)(89i)(7 + 5i)(8 - 9i) Applying the FOIL method:

    • First: 7×8=567 \times 8 = 56
    • Outer: 7×(9i)=63i7 \times (-9i) = -63i
    • Inner: 5i×8=40i5i \times 8 = 40i
    • Last: 5i×(9i)=45i25i \times (-9i) = -45i^2
  2. Simplify the expression: 5663i+40i45i256 - 63i + 40i - 45i^2 Recall that i2=1i^2 = -1, so: 45i2=45(1)=45-45i^2 = -45(-1) = 45

  3. Combine like terms: 56+4563i+40i=10123i56 + 45 - 63i + 40i = 101 - 23i

So, the simplified answer is: 10123i101 - 23i

Would you like more details or have any other questions?


Here are 5 related questions to deepen your understanding:

  1. How do you multiply two complex numbers in general form?
  2. Why is i2=1i^2 = -1 significant in complex number multiplication?
  3. Can complex numbers be divided using a similar method?
  4. What is the geometric interpretation of multiplying complex numbers?
  5. How does the result of multiplying two complex numbers compare to just adding them?

Tip: Always remember to simplify any i2i^2 terms in complex number multiplication, since they turn into real numbers!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Complex Numbers
Multiplication of Complex Numbers
FOIL Method

Formulas

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

Theorems

Properties of Imaginary Units
Distributive Property

Suitable Grade Level

High School (Grades 9-12)