Answer:
ANSWER IS BELOW
Step-by-step explanation:
f
(
x
)
=
−
1
2
x
2
+
3
x
−
1
2
Step-by-step explanation:
A quadratic function can be written in vertex form as:
f
(
x
)
=
a
(
x
−
h
)
2
+
k
where
(
h
,
k
)
is the vertex and
a
is a constant multiplier.
In our example the vertex
(
h
,
k
)
is
(
3
,
4
)
, so we can write:
f
(
x
)
=
a
(
x
−
3
)
2
+
4
Given that this passes through the point
(
1
,
2
)
, we must have:
2
=
a
(
1
−
3
)
2
+
4
=
4
a
+
4
Subtract
4
from both ends to get:
−
2
=
4
a
Divide both sides by
4
and transpose to find:
a
=
−
1
2
So our quadratic function can be written in vertex form as:
f
(
x
)
=
−
1
2
(
x
−
3
)
2
+
4
We can multiply this out and simplify as follows:
f
(
x
)
=
−
1
2
(
x
−
3
)
2
+
4
f
(
x
)
=
−
1
2
(
x
2
−
6
x
+
9
)
+
4
f
(
x
)
=
−
1
2
x
2
+
3
x
−
9
2
+
4
f
(
x
)
=
−
1
2
x
2
+
3
x
−
1
2