Question

What is the axis of symmetry for f(x)=-2x^2+20x-42

Answer 1

F(x) = -2x² + 20x - 42

This is a quadratic expression.

For a general expression   ax² + bx + c,  the axis of symmetry   x = -b/2a

Comparing -2x² + 20x - 42 to   ax² + bx + c,     a = -2, b = 20,  c= -42

Axis of symmetry,  x = -b/2a

x = -20 / (2 * -2) =  -20/-4 = 5

Therefore axis of symmetry is    x = 5.