(i)[3]
Find the coordinates of the stationary point on this curve.
(ii)[2]
Find an expression for $\frac{d^2y}{dx^2}$ and hence, or otherwise, determine the nature of the stationary point.
(iii)[3]
Find the values of $x$ for which the line $y = 6$ intersects the curve.
(iv)[1]
State the set of values of $k$ for which the line $y = k$ does not meet the curve.