Maths-
General
Easy

Question

Sage began graphing f(x) = -2x2 + 4x + 9 by finding the axis of symmetry x = -1. Explain the error Sage made?

hintHint:

For a quadratic function is in standard form, f(x)=ax2+bx+c.
Axis of symmetry x=−b/2a

The correct answer is: x = -1


    We have given the equation f(x) = -2x2 + 4x + 9
    We will first find the axis of symmetry ‘

    x = -b/ 2a

         x = -4 / 2 (-2)

    x = -4/ -4

                                                                                x = 1
    This detects the error made by sage that he finds axis of symmetry as x = -1