How do you factor completely #ab^2 - 3b^2 - 4a + 12#?

1 Answer
Don't Memorise
Jan 6, 2016

#=color(green)((b^2-4)(a-3)#

Explanation:

#ab^2 -3b^2-4a +12#

We can make groups of two to factorise this expression:
#(ab^2 -3b^2) + (-4a +12)#

#b^2# is common to both the terms in the first group, and #-4# is common to both the terms in the second group.
We can write the expression as :
#b^2(a -3) -4 (a -3)#

Now, The term #(a-3)# is common to both the terms
#=color(green)((b^2-4)(a-3)#

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