Write the equation of the axis of symmetry.

y = 3x2 + 9x - 5

x = - 3/2 (or x = - 1.5)

Step-by-step explanation:

y = 3x² + 9x - 5

by observation, we can see that this quadratic function will produce a parabolic curve (which we know is symmetric about its vertex).

Recall that for a quadratic equation in the from:

y = ax² + bx + c

the x location of the vertex (and also the axis of symmetry) is given by

x = - b/2a

in this case, b = 9 and a = 3

hence

x = - (9) / (2) (3)

x = - 9/6

x = - 3/2