Question

The graph of a quadratic function is a parabola that opens down and has a vertex of (4, 3). Which of the following could be the function?
A.
y = -x^2 +4x +3
B.
y = -x^2 +8x -13
C.
y = x^2 -4x + 3
D.
y = x^2 -8x -13

Answer 1

hint: if it opens down then it will have - before the x^2
writing it in vertex form will then show you which one it is

Answer 2

vertex form is y = (x+a)^2 + b

Answer 3

I think it is B but I am not sure

Answer 4

NM it is A

Answer 5

you sure its A?

Answer 6

From what you said I think it is atleast

Answer 7

IF vertex form is what you said then it should fit

Answer 8

Please do correct me if I am wrong though, I am honestly struggleing in algebra

Answer 9

y = -x^2 +8x -13
= - (x^2 - 8x + 13)
= -[ (x - 4)^2 -3)]

at vertex x = 4 because that gives maximum value of the function
now you can work out what y is at vertex

Answer 10

ok? y = 3
so vertex is (4,3)

so its B

Answer 11

Thanks for your help

Answer 12

yw