Question

Sketch the quadratic function ƒ(x) with a vertex at (–1, 2) and the points (0, 0) and (–2, 0). Which statement describes the parabola graph?

A) decreasing when x < 0
B) decreasing when x < –1
Eliminate
C) decreasing when x > –1
D) decreasing when x > –2

Answer 1

I believe it is C) decreasing when x > -1

Explanation:

If you plot all 3 points on a graph, you will notice that the parabola is facing downwards. This means that on the left side of the vertex, it is increasing (the y-value increases). On the right side of the vertex, it decreases (y-value decreases). Note that "decreasing" refers to the y values.

So, since the vertex's x-value is -1 (we know this from the point (-1, 2)), any x-value greater than -1 will be to the right of the vertex. For example, 0, 1, 2, 3, etc. are all greater x-values than -1, so they are all to the right of -1. Since they are on the right, that means the corresponding-values will be decreasing.

Therefore, when x > -1, the parabola is decreasing.

Answer 2

The answer is B

Explanation: