The difference of the square of a number and three times the sum of the number and 7 is more than the product of that number and 15.

select the inequality that can be used to determine the unknown number.

a.) x2 + 3x ≥ 15 + x

b.) x2 - 3x + 7 ≥ 15x

c.) x2 - 3x - 21 > 15x

d.) x2 - 3x + 21 > 15 + x

Astudent draws two parabolas on graph paper. both parabolas cross the x-axis at (–4, 0) and (6, 0). the y-intercept of the first parabola 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? write your answer as a decimal rounded to the nearest tenth