How do you factor #x^2-12x-45#?

1 Answer
EZ as pi
Jun 23, 2016

#(x-15)(x+3)#

Explanation:

Look at the colour coding to see what each part of the trinomial tells us.

#x^2 color(blue)(-) color(orange)(12)xcolor(purple)(-)color(red)(45)#

Find the factors of #color(red)(45)# which #color(purple)("subtract")# to give #color(orange)(12)#.
The signs will be #color(purple)("different")#, there must be more #color(blue)("negatives.")#
The factors of 45 which we need are 15 and 3.

#15 xx3 = 45 and15-3 = 12#

#(x-15)(x+3)#

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