SOLUTION: please show work -7i(6i-3)

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Question 53509: please show work
-7i(6i-3)
Answer by mathchemprofessor(65) About Me  (Show Source):
You can put this solution on YOUR website!
-7i(6i-3)=-42i^2+21i=(-42)x(-1)+21i=42+21i, since i^2=-1