How do you factor by grouping $x^3+6x^2-5x-30$ ?

Question

4281 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-06-08T19:03:13

$x^3+6x^2-5x-30$

$=(x^3+6x^2)-(5x+30)$

$=x^2*(x+6)-5*(x+6)$

$=(x^2-5)(x+6)$

If you allow irrational coefficients...

$=(x^2-(sqrt(5))^2)(x+6)$

$=(x-sqrt(5))(x+sqrt(5))(x+6)$

..using the difference of squares identity:

$a^2-b^2 = (a-b)(a+b)$

How do you factor by grouping x^3+6x^2-5x-30x^3+6x^2-5x-30?