Question

find the x-intercepts of the parabola with vertex (-1,-16) and y intercept (0,15), write your answer in this form (x1,y1),(x2,y2)

Answer 1

hello :
the parabola's equation is : f(x) = a(x+1)²+16
the coefficient of the squared expression in the parabola's equation is : a
but ; f(0) = 15 ...  ( y-intercepts (0,15) )

15 = a(0+1)²+16
15 =a +16

a=-1
f(x) = -(x-1)²+16

 the x-intercepts  when : f(x) =0
-(x-1)²+16=0
(x-1)² =16=4²
x-1 = 4   or x-1 = -4
x=5 or x=-3

 are  the x-intercepts 
two points : (5 , 0 )   ; (-3 ; 0)