Compute the rate of change (that is, d) of the following functions at the point x = 0: \text { i) } y=e^{x \cos x-x^{2}} \text { ii) } y=\ln \left(\frac{e^{-x^{3}}}{1+2 x^{4}}\right) (b) Using the method of separating variables, solve the following differential equation: y^{\prime}(x)=\left(x^{-1}+3\right) y \text { subject to the initial condition } y(1)=\frac{1}{5}