Question

Suppose the equation of the axis of symmetry for a quadratic function is x = -1 and one of the x-intercepts is 7. What is the other x-intercept?

Answer 1

The graph of a quadratic function is a parabola.
 The axis of symmetry of a parabola is a vertical line that divides the parabola into two congruent halves. The axis of symmetry always passes through the vertex of the parabola. The x coordinate of the vertex is the equation of the axis of symmetry of the parabola.
 Taking into account the definition above, then the other intersection with x will be:
 horizontal distance between the axis of symmetry and intersection with x:
 d = 7 - (- 1) = 7 + 1 = 8
 The second intersection will then be:
 x2 = -1-8 = -9

 Answer: 
 the other x-intercept is:
 x2 = -9