The vertex of this parabola is at (5, 5). when the x-value is 6, they-value is - 1. what is the coefficient of the squared expression in the parabola's equation?

hello:

the parabola's equation is : f (x) = a (x-5) ²-5

the coefficient of the squared expression in the parabola's equation is : a

but; f (6) = - 1

- 1 = a (6-5) ²+5

a+5=-1 ... a=-6

f (x) = - 6 (x-5) ²+5

so : a = - 6