x^2-x-12

To factorize this you need to find two numbers that have a sum of -1 and a product of -12. Start y finding the pairs of numbers the times to make -12; (-1,12), (-2,6), (-3,4), (1,-12), (3,-4), (2,-6). Next you need to see which of these combinations also add to -1. The only pair that does is (3,-4). Therefore the two numbers are 3 and -4.Therefore, x²-x-12 = (x+3)(x-4). You can then check your answer by expanding the brackets and seeing if you got the right quadratic. (x+3)(x-4) = x²+3x-4x-12 = x²-x-12.