Math Problem Statement

Perform the indicated operation & simplify. Express the answer as a complex number.

(8-12i)(-5-7i)

Solution

To perform the operation (812i)(57i)(8 - 12i)(-5 - 7i) and express the answer as a complex number, we'll use the distributive property (FOIL method):

(812i)(57i)=8(5)+8(7i)12i(5)12i(7i)(8 - 12i)(-5 - 7i) = 8(-5) + 8(-7i) - 12i(-5) - 12i(-7i)

Now, let's calculate each term:

  1. 8(5)=408(-5) = -40
  2. 8(7i)=56i8(-7i) = -56i
  3. 12i(5)=60i-12i(-5) = 60i
  4. 12i(7i)-12i(-7i)

The term 12i(7i)-12i(-7i) simplifies as follows:

12i(7i)=84i2-12i(-7i) = 84i^2

Since i2=1i^2 = -1, this becomes:

84i2=84(1)=8484i^2 = 84(-1) = -84

Now, combine all the terms:

4056i+60i84-40 - 56i + 60i - 84

Combine the real and imaginary parts:

  • Real part: 4084=124-40 - 84 = -124
  • Imaginary part: 56i+60i=4i-56i + 60i = 4i

So, the simplified form of the expression is:

124+4i\boxed{-124 + 4i}

Would you like more details or have any questions about the process? Here are some related questions for further practice:

  1. Simplify (3+2i)(45i)(3 + 2i)(4 - 5i).
  2. Find the product of (7i)(3+4i)(7 - i)(3 + 4i).
  3. Simplify (23i)2(2 - 3i)^2.
  4. Perform the operation and simplify (5+6i)(2+9i)(5 + 6i)(-2 + 9i).
  5. Multiply (12i)(3+7i)(1 - 2i)(-3 + 7i) and simplify.

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

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Multiplication of Complex Numbers

Formulas

Distributive Property (FOIL method)
Imaginary unit properties (i^2 = -1)

Theorems

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Suitable Grade Level

Advanced High School