SOLUTION: Sherry’s teacher told her that if she was foiling conjugates she would not have any imaginary parts left. She has been trying to figure out why she foiled the following conjugat

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Question 1163105: Sherry’s teacher told her that if she was foiling conjugates she would not have any imaginary parts left. She has been trying to figure out why she foiled the following conjugate and was left with an imaginary. What did she do wrong? After figuring out what she did wrong, simplify correctly.
(2-3i)
(2+3i) is the conjugate
(2-3i)(2+3i)
4+6i-6i+9i^2
4-9i^2
When I do this problem my answer comes out as 13. I know how to do this correctly but I'm not sure what the mistake was in this question, thanks!
Found 2 solutions by ikleyn, MathTherapy:
Answer by ikleyn(52794) About Me  (Show Source):
You can put this solution on YOUR website!
.

The last line  MUST  BE  COMPLETED  in this way


                4-9i^2 = 4 -9*(-1) = 4 + 9 = 13.         the final ANSWER


to eliminate any mentioning of the imaginary unit  " i "

(although  " i^2 " is just a real number  -1).




Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

Sherry’s teacher told her that if she was foiling conjugates she would not have any imaginary parts left. She has been trying to figure out why she foiled the following conjugate and was left with an imaginary. What did she do wrong? After figuring out what she did wrong, simplify correctly.
(2-3i)
(2+3i) is the conjugate
(2-3i)(2+3i)
4+6i-6i+9i^2
4-9i^2
When I do this problem my answer comes out as 13. I know how to do this correctly but I'm not sure what the mistake was in this question, thanks!
4+%2B+6i+-+6i+%2B+9i%5E2 <======ERROR exists HERE!



Then, matrix%281%2C5%2C+-+9i%5E2%2C+%22=%22%2C+-+9%28-+1%29%2C+%22=%22%2C+9%29

Finally, you have 4 + 9 = 13. Got it?