Help? Fan and medal will be given. Thank you in advance:)
Suppose a parabola has an axis of symmetry at x = -5, a maximum height of 9 and passes through the point (-7, 1). Write the equation of the parabola in vertex form.
A. y = -4(x - 5)^2 + 9
B. y = -7(x + 9)^2 - 5
C. y = -0.06(x - 5)^2 + 9
D. y = -2(x + 5)^2 + 9

Question

Help? Fan and medal will be given. Thank you in advance:) 
Suppose a parabola has an axis of symmetry at x = -5, a maximum height of 9 and passes through the point (-7, 1). Write the equation of the parabola in vertex form. 
A. y = -4(x - 5)^2 + 9
B. y = -7(x + 9)^2 - 5
C. y = -0.06(x - 5)^2 + 9
D. y = -2(x + 5)^2 + 9

anonymous · Answer

i think it's b or c

campbell_st · Answer

well the axis of symmetry and the max height give you the vertex... (-5, 9)

and given it says max height... the parabola is concave down... 

so the vertex form  you will use is

$$y = -a(x -h)^2 + k$$

where (h, k) is the vertex

to find the value of a, substitute the point (-7, 1) and then solve for a

ray1998 · Answer

Thank you :) I think that's all I need to figure out how to solve it.

ray1998 · Answer

Oh! Sorry, did I mistype something?

campbell_st · Answer

no... I just checked... everything is ok... the answer should become obvious is you substitute correctly

ray1998 · Answer

Oh, okay. Thank you :)