if anyone is still confused why i used differentiation i found smthing for u@Shavi Masee
got it with the help of AI cus i forget about turning point silly me
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AND CHECKING WITH DESMOS DRUMROLL PLEASE
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@cheesynooby
can u teach me how to use the element of symbol for domain and range thanks

in the working out i replaced f'(x) with 0 for the stationary point (that was the word i was looking for)
@cheesynooby is there a better way to solve it that doesn't include derivatives (for shavi to understand)