Find the limits for integrals $\int\int f(x,y) \,dy \, dx$ and $\int\int f(x,y)\,dx\,dy$ and compute the integral over the region, based on the function $f(x,y) = 3x^2y$.
Region = triangle inside the lines $x=0$, $y=1$, $y=2x$.
To find what the limits of my inner integral should be, I tried to sketch it. My problem was, how do I sketch a triangle when the only information I have is $x=0, y=1, y=2x$. I have no boundary for $x$?