The vertex of this parabola is at (4,-3). When the x-value is 5, the y-value is at -6. What is the coefficient of the squared expression in the parabola's equation ?

A. 3
B. -2
C. -3
D. 2

Question

The vertex of this parabola is at (4,-3). When the x-value is 5, the y-value is at -6. What is the coefficient of the squared expression in the parabola's equation ?

A. 3
B. -2
C. -3 
D. 2

anonymous · Answer

Help me please :(

sherribelle · Answer

Use the formula:
y = a(x - h)^2 + k
vertex = (h,k)

anonymous · Answer

but how do i know which numbers to plug  in to which variable ?

sherribelle · Answer

The vertex = (h,k)
So y = -6
a = is the variable you're trying to find
x = 5
h = 4
k = -3

sherribelle · Answer

So whatever the vertex is, is what you plug into h and k.
It should look like:
-6 = a(5-4)^2 - 3

sherribelle · Answer

The app Mathway is really helpful once you have everything set up.

anonymous · Answer

so i got 3 ?

sherribelle · Answer

Mathway got -3, let me work it out on paper.

sherribelle · Answer

I got 3 as well.