find the equation of a parabola whose vertex is at (-1,7), whos axis of symmertry is x=-1, and who's y-intercept is (0,10). write your answer in vertex form.
write in vertex form first: y = a(x + 1)^2 + 7
The coefficient "a" is there because knowing the vertex isn't enough to determine the equation. We can plug in the point (0, 10):
10 = a + 7
a = 3
So, the equation is y = 3(x+1)^2 + 7.