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Express (4 - 5i)(5 + 5i)(2 - 7i) in the form a + bi, where a and b are integers and i^2 = -1.

 May 3, 2022
 #1
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You can just expand it like i was a variable instead of a special number, and use the fact i^2 = -1 occasionally to reduce the power.

 

\(\quad(4 - 5i)(5 + 5i)(2 - 7i)\\ =(20 - 25i + 20i - 25i^2 )(2-7i)\\ = (20 - 5i -25i^2)(2 - 7i)\\ = (45 - 5i)(2 - 7i)\\ \)

 

Can you continue from here, doing what I just did?

 May 3, 2022

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