Question 26: Given the function \(y = f\left( x \right)\) whose derivative is \(f’\left( x \right) = x{\left( {x + 1} \right)^ 2}\left( {x – 1} \right)\). How many extremes does the function \(y = f\left( x \right)\) have?

We have \(f’\left( x \right)\) that changes sign when x passes 0 points; first.

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