How do you factor by grouping #a^3 - a^2 - 8a + 8#?

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Answer 1 · 2015-05-24T23:07:37

#a^3-a^2-8a+8#

#=(a^3-a^2)-(8a-8)#

#=a^2(a-1)-8(a-1)#

#=(a^2-8)(a-1)#

#=(a^2-(2sqrt(2))^2)(a-1)#

#=(a-2sqrt(2))(a+2sqrt(2))(a-1)#

....using the identity #(p^2-q^2) = (p-q)(p+q)#