Factorise x^2-7x+12

First write down all the factor pairs of 12 (1,12) (-1,-12) (3,4) (-3,-4) (6,2) (-6,-2).

From these factors, find a pair that, when added together, is equal to -7.

In this case the correct pair would be -3 and -4 as -3+-4 = -7

the solution is therefore (x-3)(x-4)