For the function [tex]f(x)=2x^2 +20x-42[/tex]
We can use the formula for the axis of symetry, which is [tex]x= \frac{-b}{2a} [/tex]
With the values substituted, we get...
[tex] \frac{-20}{2(-2)} =5[/tex]
Therefore the axis of symmetry is [tex]x=5[/tex]
