Math Problem Statement

(4 + 5i)(8 + 7i)

Solution

To solve (4+5i)(8+7i)(4 + 5i)(8 + 7i), we use the distributive property (FOIL method) for multiplying complex numbers. Let's walk through the steps:

  1. Multiply the real parts:
    4×8=324 \times 8 = 32

  2. Multiply the outer terms:
    4×7i=28i4 \times 7i = 28i

  3. Multiply the inner terms:
    5i×8=40i5i \times 8 = 40i

  4. Multiply the imaginary parts:
    5i×7i=35i25i \times 7i = 35i^2

Since i2=1i^2 = -1, 35i2=35×(1)=3535i^2 = 35 \times (-1) = -35.

Now, sum all the parts:

  • Real part: 3235=332 - 35 = -3
  • Imaginary part: 28i+40i=68i28i + 40i = 68i

Thus, the simplified expression is:
(4+5i)(8+7i)=3+68i(4 + 5i)(8 + 7i) = -3 + 68i

Would you like more details or have any other questions? Here are some related questions:

  1. How do you multiply two complex numbers?
  2. What is the significance of i2=1i^2 = -1 in complex number calculations?
  3. How can we generalize this method for any complex number multiplication?
  4. What are the geometric interpretations of multiplying complex numbers?
  5. Can the result of multiplying two complex numbers ever be a purely real number?

Tip: When multiplying complex numbers, always remember to apply i2=1i^2 = -1 to simplify the result.

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Algebra
Distributive Property (FOIL Method)
Imaginary Numbers

Formulas

(a + bi)(c + di) = (ac - bd) + (ad + bc)i

Theorems

i^2 = -1

Suitable Grade Level

Grades 10-12