# Thread: I forgot how to do this...

1. ## I forgot how to do this...

Problem: "The graph of a quadratic function has a vertex at (-3,7) and a Y-intercept of 18. Name any other point on the parabola."
Y-7= a(x+3)^2 is the only thing that comes to mind, and It's not really helping me solve this question...

Identical problem: "Find a particuar equation of the quadratic function that passes through a vertex of (5,-1) and the point (8,-28)."

Any help would be much appreciated.

Problem: "The graph of a quadratic function has a vertex at (-3,7) and a Y-intercept of 18. Name any other point on the parabola."
Y-7= a(x+3)^2 is the only thing that comes to mind, and It's not really helping me solve this question...

Identical problem: "Find a particuar equation of the quadratic function that passes through a vertex of (5,-1) and the point (8,-28)."

Any help would be much appreciated.
y = a(x+3)^2 + 7

(0,18) is the y-intercept ...

18 = a(0+3)^2 + 7

solve for "a"

3. I'm just checking with with you (or anyone really), if that's okay. (Sorry, it's the beginning of the year and I forgot nearly everything over the summer.) Does a = -5?

Work:
18= a(9) + 7
2 = a + 7
-5 = a

I'm just checking with with you (or anyone really), if that's okay. (Sorry, it's the beginning of the year and I forgot nearly everything over the summer.) Does a = -5?

Work:
18= a(9) + 7
2 = a + 7
-5 = a
you forgot how to solve these, too ? ...

18 = 9a + 7

subtract 7 first ...

11 = 9a

divide by 9 ...

11/9 = a