Mathematics
OpenStudy (anonymous):

Calculate the area bounded by f(x)=3x, the x-axis and the vertical lines x=-1 and x=3. Sketch the region in the xy plane

The area under a curve like $$f(x)$$ is found by taking an integral of that function. The bounds in this case are -1 to 3, so you can say: $A = \int_{-1}^3 f(x)dx = \int_{-1}^3 3xdx OpenStudy (shadowfiend): Sorry, that's: \[A = \int_{-1}^3 f(x)dx = \int_{-1}^3 3xdx$