Answer:
Intercepts at (0,7) and (0,03)
Vertex at (2,-25)
Explanation:
Axis of symmetry is -b/2a = -(-4)/2(1) = 4/2 = 2 x=2
Plug x=2 into the equation and get 2^2-4(2)-21 = 4-8-21 = -25
Vertex is (2,-25)
Factor the equation (x-7)(x+3)
Set x-7=0, x=7
set x+3=0, x= -3
x intercepts at 7 and -3