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(i)

Differentiating the given equation with respect to x,

(ii)

(iii)

When $latex \frac{dy}{dx} = 0, \frac{d^2y}{dx^2} = -1 <0$
Thus we conclude that the turning point is a maximum point.

### KS Comments:

Some students can still get the implicit differentiation wrong. (iii) actually is very simple if students do not overthink and trust in what they understand.

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