Observe the graph :
\From graph the vertex is
.
The vertex and one additional point on the graph of the quadratic function.
\ Quadratic function in vertex form
.
Substitute
,
in
.


Find the value of
.
The parabola passes through point
.
Substitute for
,
in
.
\
\ \
Substitute for
,
and
in 

The quadratic function is
.
.
The quadratic function is
.