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 $(p^2-q^2) = (p-q)(p+q)$

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