Question

What are the vertex and x-intercepts of the graph of y = x2 – 4x – 21? Select one answer for the vertex and one for the x-intercepts. A. x-intercepts: (–3, 0), (7, 0) B. x-intercepts: (3, 0), (7, 0) C. x-intercepts: (3, 0), (–7, 0) D. Vertex: (2, 13) E. Vertex: (2, –25) F. Vertex: (–2, –9)

Answer 1

To find x-intercept ,let y=0

0=x²-4x-21

(x+3)(x-7)=0

x=-3 or x=7

(-3;0) or (7;0)

To find vertex

x=

`( - b)/(2a) = x`

x=4/2=2

y=(2)²-4(2)-21=-25

(2;-25)

choose A and E