The axis of symmetry of the given function is; C: x = 6
How to find the axis of symmetry of a function?
We are given that;
f(x) = -(x + 9)(x - 21)
Using the multiplicative distributive property, we have;
f(x) = -(x² - 21x + 9x - 189)
f(x) = -x² + 21x - 9x + 189
f(x) = -x² + 12x + 189
We know that;
Axis of symmetry is x = -b/2a
Thus;
x = -12/2(-1)
x = -12/-2
x = 6
In conclusion, the axis of symmetry is 6.
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