SOLUTION: perform the indicated operation and write answer in standard form please (3+9i)(3-9i)

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Question 53507: perform the indicated operation and write answer in standard form please
(3+9i)(3-9i)
Answer by mathchemprofessor(65) About Me  (Show Source):
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(3+9i)(3-9i)=3^2-(9i)^2=9-(81i^2)=9-81(-1)=9+81=90, using (a+b)(a-b)=a^2-b^2 and i^2=-1