0=x^2+4x+1. Khan academy

Now, to find 'x' you will apply the Null Factor Law. This means you will now let 'x' = 0, and simply move the -2 over to the other side to find your answer. Note: since we are using a perfect square, x will only have one value since there is only one answer (x-2) in the brackets, meaning in this case we can ignore the exponent (as the answers will be the same). If there was more than one answer in the bracket (e.g. (x-4) and (x-6)), then we would apply Null Factor Law to both brackets and solve for x.

(x−2)=5

x=5+2

x=7

The answer would be 24mm