If s is a real number, then what is the smallest possible value of 2s^2 - 8s + 19 - 7s^2 - 8s + 20?
Combine terms –5s2 – 16s + 39
If you set this equal to y and graph it, you see that
the curve is a parabola that opens downward.
When a parabola opens upward, the smallest y-value is the vertex.
When a parabola opens downward, there is no smallest value.
.