The maximum value of function f (x) = 2x ^ 3-6x ^ 2-18x + 7 is?

The maximum value of function f (x) = 2x ^ 3-6x ^ 2-18x + 7 is?

f'(x)=6x²-12x-18=0
x=3,x=-1
F '(x) opening upward
So X3, f '(x) > 0, f (x) is an increasing function
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