Find the derivative of the polynomial w.r.t x. Equate the derivative to 0.

The value of x obtained, when being put in in the polynomial will give its max.(A<0)

or min. value(A>0).

After this, the graph can be drawn easily.

For ex;

y=2x^2+12x+16

Derivative=4x+12=0

which gives x=-3

On putting  x=-3 in

y=2x^2+12x+16, we get min. value of this polynomial.

which comes out to be -2.

Plzzz rate me if this was helpful.