Question 999194
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simplify (6+3i)(2i-4)-(4i+5i) 
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(6 + 3i)*(2i - 4) - (4i + 5i) = 6*(2i) - 24 + (3i)*(2i) -4*(3i) - (9i) = 12i - 24 + 6i^2 - 12i - 9i = -24 - 6 - 9i = -30 - 9i.


You make all calculations as if &nbsp;<B>i</B>&nbsp; is a regular symbol.
Remember that {{{i^2}}} = -1, &nbsp;and every time you have &nbsp;{{{i^2}}}, replace it by &nbsp;(-1).