How do you factor by grouping $3x^3 + 15x^2 - 4x - 20$ ?

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Answer 1 · 2015-05-03T12:26:25

Collect $x$ betwen the first and third term and $5$ between the second and fourth:
$x(3x^2-4)+5(3x^2-4)=$

collect #(3x^2-4);

$=(3x^2-4)(x+5)$

How do you factor by grouping 3x^3 + 15x^2 - 4x - 203x^3 + 15x^2 - 4x - 20?