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

1 Answer
Feb 3, 2016

Answer:

#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))#