# Pre-Cal

Perform the operation and write the result in standard form.

(2-3i)(5i) over 2+3i

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1. (2-3i)(5i) over 2+3i
= 5i(2-3i)/(2+3i)
multiply top and bottom by 2-3i

= 5i(4 - 12i + 9i^2)/(4-9i^2)
= 5i(-13 - 12i)/13
= (-65i - 60i^2)/13
= (60 - 65i)/13

or 60/13 - 5i if by standard form you mean a + bi

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2. ok, Kim ,I messed up in the arithmetic

but, if you understand what I did, you should be able to fix it yourself.

hint: the error is from
= 5i(4 - 12i + 9i^2)/(4-9i^2) to
= 5i(-13 - 12i)/13

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3. YOU SHOULD KNOW HOW TO DO THIS!

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