SOLUTION: (1-i)(7+2i)

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Question 612999: (1-i)(7+2i)
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
%281-i%29%2A%287%2B2i%29 Start with the given expression.


%281%29%287%29%2B%281%29%282i%29%2B%28-i%29%287%29%2B%28-i%29%282i%29 FOIL.


7%2B2i-7i-2i%5E2 Multiply.


7%2B2i-7i-2%28-1%29 Replace i%5E2 with -1. Note: i%5E2=-1.


7%2B2i-7i%2B2 Multiply.


9-5i Combine like terms.


So %281-i%29%2A%287%2B2i%29=9-5i.


So the expression is now in standard form a%2Bbi where a=9 and b=-5