Question

A student 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.

Answer 1

∆a = 1/2

Explanation:

parabolas cross the x-axis at (-4, 0) and (6, 0)

y = a(x + 4)(x - 6)

At the y-intercept x = 0

y = a(0 + 4)(0 - 6)

y = -24a

-----------------------

y-intercept of the first parabola is (0,–12)

-12 = -24a

a = 1/2

-----------------------

y-intercept of the second parabola is (0, -24)

-24 = -24a

a = 1

----------------------

What is the positive difference between the a values

∆a = 1 - 1/2

∆a = 1/2