How do you factor #2a^2-9a-18#?

1 Answer
George C.
May 9, 2016

#2a^2-9a-18=(2a+3)(a-6)#

Explanation:

Use an AC method:

Find a pair of factors of #AC=2*18 = 36# which differ by #B=9#.

The pair #12, 3# works in that #12-3=9# and #12*3=36#

Use this pair to split the middle term and factor by grouping:

#2a^2-9a-18#

#=2a^2-12a+3a-18#

#=(2a^2-12a)+(3a-18)#

#=2a(a-6)+3(a-6)#

#=(2a+3)(a-6)#

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