# Calculating Double Integral – Finding integration limits and the integral – Exercise 3907

Exercise

Calculate the double integral

$$\int\int_D (x^2+y^2)dx dy$$

When D is a parallel with the sides

$$y=x, y=x+a, y=a, y=3a, a>0$$

$$\int\int_D (x^2+y^2)dx dy=14a^4$$