How do you multiply #(- 18- 7i ) ( 5+ - 9i )#?

1 Answer
smendyka
Aug 1, 2017

See a solution process below:

Explanation:

To multiply these two terms you multiply each individual term in the left parenthesis by each individual term in the right parenthesis.

#(color(red)(-18) - color(red)(7i))(color(blue)(5) + color(blue)(-9i)) =>#

#(color(red)(-18) - color(red)(7i))(color(blue)(5) - color(blue)(9i))# becomes:

#(color(red)(-18) xx color(blue)(5)) + (color(red)(18) xx color(blue)(9i)) - (color(red)(7i) xx color(blue)(5)) + (color(red)(7i) xx color(blue)(9i))#

#-90 + 162i - 35i + 63i^2#

We can now combine like terms:

#-90 + (162 - 35)i + 63i^2#

#-90 + 127i + 63i^2#

If necessary, we can write the expression in standard form:

#63i^2 + 127i - 90#

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