Stretch Your Thinking ST 1. Suppose that f{3:_ y] is a differentiable function such that HQ, 1) = 4 and fzl 1] = 1. In addition, an equation for the tangent line to the level curve at. 3;) = 4 in the 3yplane at the point {2, 1} is given by 23: - 41; = U. Give an example of such a function an-y). [5 marks]