What are the vertex and x-intercepts of the graph of the function below? y = x2 - 4x - 21 A. Vertex: (2, -25); Intercepts: x = 3, -7 B. Vertex: (2, 17); Intercepts: x = -3, 7 C. Vertex: (2, 17); Intercepts: x = 3, -7 D. Vertex: (2, -25); Intercepts: x = -3, 7

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alykj707

Middle School

What are the vertex and x-intercepts of the graph of the function below?
y = x2 - 4x - 21
A. Vertex: (2, -25); Intercepts: x = 3, -7
B. Vertex: (2, 17); Intercepts: x = -3, 7
C. Vertex: (2, 17); Intercepts: x = 3, -7
D. Vertex: (2, -25); Intercepts: x = -3, 7

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(Based on todays review)

Esme1995

Answer:
Vertex: (2, -25); Intercepts: x = -3, 7
Step-by-step explanation:
$y = x^2 - 4x - 21$
Lets find out the vertex and the x intercepts
To find out the vertex we use formula
$x=\frac{-b}{2a}$
The value of a= 1, b=-4. Plug in the values
$x=\frac{-(-4)}{2(1)=2}$
Substitute x=2 and find out y
$y = 2^2 - 4(2) - 21=-25$
So vertex (2,-25)
Now we find out x intercepts, replace y with 0 and solve for x
$0 = x^2 - 4x - 21$
we find out two factors whose product -21 and add upto -4
the factors are -7 and 3
$0 = (x-7)(x+3)$
$x-7=0, x=7$
$x+3=0, x=-3$
x intercepts are -3,7
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lisboa

Verified answer

I think is D.vertex(2_25);intercept:x=_3,7
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