Question

A parabola y= ax^2 + k

passes through the points (-1, -3) and (3, 13). Find the values of a and k

Answer 1

use vertex form of parabola:

y=a%28x-h%29%5E2%2Bk....if vertex (0,7), we have

y=a%28x-0%29%5E2%2B7

y=ax%5E2%2B7......use point (3,2) to find a

2=a%2A3%5E2%2B7

2=9a%2B7

2-7=9a

-5=9a

a=-5%2F9

so, your equation is: y=-%285%2F9%29x%5E2%2B7

Explanation: