f(x)=x^3=12x-24

f'(x)=3x^2+12=0
3x^2=-12
x^2=-4

what is x. would it be x=-2 and 2

because i have to find the interval where the function is increasing or decreasing.

i already know how to find the answer but i just got confused on finding the zeros first

<<f(x)=x^3=12x-24
f'(x)=3x^2+12=0
3x^2=-12
x^2=-4

what is x. would it be x=-2 and 2

.. i have to find the interval where the function is increasing or decreasing.>>

If the symbol after the x^3 is supposed to be a +, and not an = (as you typed it), then f'(x) is always positve.

Setting f'(x) = leads to an imaginary answer: x = i or -i.

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