Question

What is the vertex of y = x2 + 4x – 7?

O(-4,-7)
O (2, 5)
0 (-2, -19)
0 (-2, -11)

Answer 1

2
,
0
)
Method 1:
y
=
x
2
−
4
x
+
4

complete the square to get:
y
=
(
x
−
2
)
2
pick out the x value (2), and the y value (o)
to get:
(
2
,
0
)
method 2:
y
=
x
2
−
4
x
+
4

d
y
d
x
=
2
x
−
4

let
d
y
d
x
=
0
as the vertex is when the gradient of the curve is 0.
to get
x
=
2

substitute that into the original equation to get
(
2
,
0
)