Answer:
The axis of symmetry is x = 6
Step-by-step explanation:
To find this, first find the two x-intercept values and then take the average. This will always be the line of symmetry.
x + 9 = 0
x = -9
x - 21 = 0
x = 21
Now take the average of these two numbers.
(-9 + 21)/2
12/2
6
