Question

What is the equation for the graph shown below?

A. x^2 – 3x – 25
B. x^2 – 7x – 25
C. x^2 + 7x – 21
D. x^2 + 2x - 25

Answer 1

9514 1404 393

Answer:

D. x^2 + 2x - 25

Explanation:

The y-intercept is -25, eliminating choice C. The axis of symmetry is negative, eliminating choices A and B. (The axis of symmetry is x = -b/(2a), so the coefficient of x must be positive for a negative axis of symmetry.)

The only viable choice is D:

x^2 + 2x - 25

_____

Additional comment

Though the y-intercept is in the right place, it seems to me the vertex and x-intercepts are slightly too far left for the given equation. That is why I chose to eliminate non-viable answers, rather than try to determine the equation directly. That is also why I elected to show a better graph of equation D.