How do you write y=x^3+6x^2-25x-150y=x3+6x225x150 in factored form?

1 Answer
Apr 21, 2018

y = (x-5)(x+5)(x+6)y=(x5)(x+5)(x+6)

Explanation:

The difference of squares identity can be written:

A^2-B^2 = (A-B)(A+B)A2B2=(AB)(A+B)

We will use this with A=xA=x and B=5B=5.

Given:

y = x^3+6x^2-25x-150y=x3+6x225x150

Note that the ratio between the first and second terms is the same as that between the third and fourth terms.

So this cubic will factor by grouping:

y = x^3+6x^2-25x-150y=x3+6x225x150

color(white)(y) = (x^3+6x^2)-(25x+150)y=(x3+6x2)(25x+150)

color(white)(y) = x^2(x+6)-25(x+6)y=x2(x+6)25(x+6)

color(white)(y) = (x^2-25)(x+6)y=(x225)(x+6)

color(white)(y) = (x^2-5^2)(x+6)y=(x252)(x+6)

color(white)(y) = (x-5)(x+5)(x+6)y=(x5)(x+5)(x+6)