How do you factor the expression 4a ^3 + 15a ^2 - 4a?

1 Answer
Alan P.
Feb 3, 2016

4a^3+15a^2-4a= color(green)(a(4a-1)(a+4))

Explanation:

First remove the obvious common factor of color(red)(a)
color(white)("XXX")color(red)(a)(color(blue)(4)a^2+color(orange)(15)acolor(cyan)(-4))

Use the quadratic formula
or
check for factors of color(blue)(4) which when cross multiplied by factors of color(cyan)(-4) have a sum of color(orange)(15)
to get
color(white)("XXX")color(red)(a)(color(purple)(4a-1))(color(brown)(a+4))

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