Question

How do you solve this?

Answer 1

You have correctly found a=2, b=5, c=3.
You know a > 0, so the parabola will open up.
If the parabola opens up, the vertex is a minimum.

Use the formula for the axis of symmetry.
.. x = -b/(2a) = -5/(2*2) = -5/4
.. f(-5/4) = 2(-5/4)^2 +5(-5/4) +3 = -1/8
The vertex is (-5/4, -1/8).

Use the formula for the discriminant.
.. b^2 -4ac = 5^2 -4*2*3 = 25 -24 = 1
This is positive and a perfect square, so there are 2 real roots. They are (1) rational and unequal.

Use the quadratic formula to tell you the roots.
.. x = -b/(2a) ±(√discriminant)/(2a)
.. = -5/4 ±√1/(2*2)
.. = -5/4 ±1/4
.. = {-3/2, -1}