Find the product z1z2 in standard form. (Simplify your answer completely.) z1 = 9 + 3i, z2 = −9 + 3i

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Step-by-step explanation:

These are "complex numbers" because they have the imaginary number, i, in the expression.

The 9 (and the -9) is the real part and the 3i is the imaginary part. But when you add or subtract, multiply or divide them you can manipulate them just as if the i was a variable (like x or n or y) If you learned to multiply

(x+2)(x+5)

= x^2 + 7x + 10

This problem will work the same way. You may have learned "FOIL" or using a box to multiply two binomials (two-piece things like x+2)

**SUPER IMPORTANT NOTE: i^2 is equal to -1

These particular complex numbers are called conjugates which means they have the same 'pieces' the 9 and the 3i, with only one sign different. So there is a short cut for this problem and the imaginary number falls out and we get a real number answer. This doesn't happen for every question, only when you multiply conjugates, but the method shown here works for multiplying complex numbers all the time.

1) 2/5

2) zero=0/1

3) zero=0/2

4) -4/5

5) undefined=3/0