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First derivative test: find the error

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Problem

Pamela was asked to find where h(x)=x36x2+12x has a relative extremum. This is her solution:
Step 1: h(x)=3(x2)2
Step 2: The solution of h(x)=0 is x=2, so x=2 is a critical point.
Step 3: h has a relative extremum at x=2.
Is Pamela's work correct? If not, what's her mistake?
Choose 1 answer: