. Find the derivative f' (x) of each of the following functions. \text { (a) } f(x)=\frac{\sqrt{x}+e^{3 x}}{x^{2}+x+1} \text { (b) } f(x)=e^{x^{3}} \cdot \ln \left(x-x^{2}\right) \text { (c) }

f(x)=\left(x^{4} \cdot \ln x\right)^{21} \text { (d) } f(x)=\frac{x^{2} \cdot e^{x}}{x^{2}+1}