SOLUTION: Hi! Thanks for your help Do you know if there's an online tool that generates a quadratic formula given the vertex and one point? I know the parabola goes through (-1,3) and the

Question 888820: Hi! Thanks for your help
Do you know if there's an online tool that generates a quadratic formula given the vertex and one point?
I know the parabola goes through (-1,3) and the vertex is (2, -4). I tried this:
f(-1)=3=a(-1-2)^2 - 4 ==>I got a=7/9...then I did this
f(x)=7/9(x-2)^2+-4. And so I'm supposed to give answer in standard form.
I got 7/9x^2 - 3+1/9x + 7+1/9. An online program says my answer is wrong
(I'm 53 yr old - just trying to learn math. Thanks!)
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
google "vertex and point"
You will get many ways to do it.
y=a(x-h)^2+k
where (h,k) is the vertex, substitute for x,y,h and k
3=a(-1-2)^2-4
3=9a-4
7=9a
a=7/9
solve for a
Substituting into the original again for a and the vertex
y=7/9(x-2)^2-4
Good so far
y = 7/9x^2-28/9x-8/9
Don't give up 53 is young.

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