Question

The graph of the function f(x) = ax2 + bx +c (where a, b, and c are real and nonzero) has two x-intercepts. Explain how to find the other x-intercept if one x-intercept is at (-b/a2 +3,0)

Answer 1

Recorded response:

The axis of symmetry is  -b/2a

The x-intercept shown is 3 units away from the axis of symmetry.

The other x-intercept also must be 3 units away from the axis of symmetry but on the opposite side.

Subtract 3 from the axis of symmetry.

The other x-intercept is  (-b/2a-3,0)

Answer 2

-b/2a is the formula to find the vertex of a parabola. If one of the intercepts is at (-b/2a + 3, 0), the other one must be at (-b/2a - 3, 0), since the two x-intercepts have to be the same distance from the vertex.