How many different non-congruent isosceles triangles can be formed by connecting three of the dots in a 4 x 4 square array of dots?

Astudent draws two parabolas both parabolas cross the x axis at (-4,0) and (6,0) the y intercept of the first parabolas is (0,-12). the y intercept of the second parabola is (0,-24) what is the positive difference between the a values for the two functions that describe the parabolas