Start with the x intercepts. You need to factor the original function. y = x^2 - 4x - 21 y = (x - 7)*(x + 3) These are the correct factors.
The two roots are x = 7 x = - 3
So the two points you want are (7,0) and (-3,0) That makes the answer C <<<<========
The vertex is a little harder. You need to complete the square to get it. (I take it you don't know any calculus yet. y = x^2 - 4x - 21 y = (x^2 - 4x + ... ) - 21 y = (x^2 - 4x + 4) - 21 - 4 y = (x - 2)^2 - 25
The vertex is (2,- 25) The answer is B <<<<<<=======
