How do you simplify #(-10i)(9i)+8#?

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Answer 1 · 2018-08-08T01:39:06

#98#

#(-10i)(9i) + 8#

First, do multiplication:
#=-90i^2 + 8#

We know that #i^2# equals to #-1#:
#=-90(-1) + 8#

Simplify:
#=90 + 8#

#=98#

Hope this helps!

Answer 2 · 2018-08-08T01:45:08

#color(magenta)((-10i) * (9i) + 8 = 98#

#color(red)(i = sqrt(-1)), " " color(maroon)(i^2 = (sqrt-1)^2 = -1#

#(-10i) * (9i) + 8 = (-90 i^2) + 8 =( -90 * -1) + 8 #

#=> 90 + 8 = 98#

Answer 3 · 2018-08-08T01:57:30

#98#

We can multiply first to now get

#-90i^2+8#

Recall that #i^2=-1#. With this simplification, we now have

#90+8#, which simplifies to #98#.

Hope this helps!