# Math Help - Factorising

1. ## Factorising

Please help in factorising this polynomial.

y = 2x^3 - x^2 - 8x + 4

also x + 2 is a factor
i used the remainder theorem and then long divided the equation
and i ended up with..

(x+2)(2x+1)(x-3)

help? lol
many thanks

2. Originally Posted by raiden
Please help in factorising this polynomial.

y = 2x^3 - x^2 - 8x + 4

also x + 2 is a factor
i used the remainder theorem and then long divided the equation
and i ended up with..

(x+2)(2x+1)(x-3)

help? lol
many thanks
Correction *Rayden not Raiden.

Anyways,
You have,
$2x^3-x^2-8x+4$
Group terms as,
$(2x^3-8x)-(x^2-4)$
Factor,
$2x(x^2-4)-(x^2-4)$
Factor again,
$(x^2-4)(2x-1)$
Factor again,
$(x+2)(x-2)(2x-1)$