Shortcut for Factoring Polynomials

**dumluck** · March 20th 2011, 05:18 AM

Hi,
Quick question.

Say we have a polynomial $k^2 + k - 12$ , one can use FOIL to find the factors.

However, is there a shortcut for doing the opposite.

i.e. I have $(k-3)(k+4)$ but want to find the polynomial? What confused me is that $- 3.-4$ will give -12 but so will $+3.-4$ .

Thanks

**janvdl** · March 20th 2011, 05:20 AM

Originally Posted by dumluck

Hi,
Quick question.

Say we have a polynomial $k^2 + k - 12$ , one can use FOIL to find the factors.

However, is there a shortcut for doing the opposite.

i.e. I have $(k-3)(k+4)$ but want to find the polynomial? What confused me is that $- 3.-4$ will give -12 but so will $+3.-4$ .

Thanks

A minus times a minus cannot give you a minus. It gives you a plus.

-3 x -4 = +12

**Plato** · March 20th 2011, 05:46 AM

Originally Posted by dumluck

Say we have a polynomial $k^2 + k - 12$ , one can use FOIL to find the factors.
However, is there a shortcut for doing the opposite.
i.e. I have $(k-3)(k+4)$ but want to find the polynomial? What confused me is that $- 3.+4$ will give -12 but so will $+3.-4$