Hello I'm a student how to figure out how to solve these types of problems and I haven't found any good resources on it. A specific problem I'm working on is this:
Let $R$ be the lamina with density $1/4$ bounded by $y\geq0$, $x\geq0$, and $y=2-7x^2$. Set up the integral for Moment $M_y$, using slices parallel to the $y$ axis.
The answer it gives is $$\int_{0}^{\sqrt{2/7}}\frac{1}{4}x(2-7x^2)dx$$ but I have no idea how they got this solution. Any help would be much appreciated.