Solve x^(2)-x-12

We must factorise. Find factor pairs of -12;1,-12;-1,12;2,-6;-2,6;3,-4;-3,4. Out of the pairs, we must find the pair that will add up to -1 - this is because of the '-x' part of the equation. The answer is 3 and -4. Now use this to factories; (x+3)(x-4). Check by expansion. Now make this equal to zero and solve for x; x=-3, x=4.