Question

Write a quadratic function in standard form that models the table.

(please be quick)

Answer 1

y = -x² - 2x + 15

Explanation:

We can see that upto the x-value of -1, the y-value increases, and after -1, the y-value decreases. This tells us both that (-1, 16) is the vertex and that the function opens downwards.

The typical vertex form for quadratic equations is:

y= a(x-h)² + k where (h,k) is the vertex.

Replace the vertex (-1,16) for (h,k)

y = a (x+1)² +16

To find a, replace any value from the table. Let's use (3,0).

0 = a (3+1)² +16

0 = a (4)² + 16

0 = 16a + 16

-16 = 16a

a = -1

Now, insert that a into our equation...

y = -13/16 (x+1)² +16

Then simplify:

y = -1 (x² +2x +1) + 16

y = -x² -2x -1 +16

We get our answer:

y = -x² - 2x + 15