You must find your x-intercepts (or roots) by factoring.
4x2+2x-12=0 .... Slide and divide your "a" value.
x2+2x-48=0 .... Find two numbers that, when multiplied, equal your c value, AND when added, equal your b value. (These numbers are 8 and -6.) Put them in the form below.
(x + 8)(x - 6) = 0 ... Redistribute your a-value by dividing the two number you found by it.
(x + 8/4)(x + 6/4) = 0 ... Simplify the fractions, you will come up with the numbers 2 and 3/2. Find numbers that will make (x +2) or (x - 3/2) equal zero. (These numbers are -2 and 3/2.)
The roots of this quadratic equation are (-2, 0) and (3/2, 0).