If $$y=(x-1)^2(x-2)^3(x-3)^5$$, then $$\frac{d y}{d x}$$ at $$x=4$$ is equal to

If $$2^x+2^y=2^{x+y}$$, then $$\frac{d y}{d x}$$ is

If $$y=2 x^{n+1}+\frac{3}{x^n}$$, then $$x^2 \frac{d^{2 y}}{d x^2}$$ is

If $$(x e)^y=e^y$$, then $$\frac{d y}{d x}$$ is