=2(x+9/4)^2-8 1/8+34

Because x=(x 1+x2)/2 is the symmetry axis of parabola.

The symmetry axis of this parabola is x=-9/4.

So x 1+x2=-9/2.

Substitute x=-9/2 into the analytical formula:

y=2*(-9/2)^2+9*(-9/2)+34

=8 1/2-8 1/2+34

=34