So you find out what two numbers add up to 5 and multiply to make -12 so since -12 is negative we know that the two numbers have to be diffarent signs (- times+=-)
also we see that the X^2 term is 2x^2 so we can use the 2 so the factored out form is (2x+3)(x-4) because the 2x times -4=-8x the 3 times the x=3x add them together and get 3x+(-8x)or 5x which is our middle term and -4 times 3 =-12 which is our last term