=> (x - m)(x - n) = 0 where m*n = 12 and m + n = a
the only two consecutive integers that multiply to give 12 is 3 and 4.
thus a = 3 + 4 = 7
The reason i dont like this method is because there is guessing involved at the end. with 12 it wasnt so bad, but if our number was a lot larger than 12, we might have had a rough time thinking of two consecutive integers to multiply and get it.
I'm sure another mathematician will come up with a better way to do this soon