If $\int_1^a (2x + 1) dx = 5$, then the sum of the values of $a$ is..

The area of the shaded region is ... sq.units.

$\int_0^3 \sqrt{9 - x^2} dx = $

The particular solution of the differential equation $xdy + 2ydx = 0$, when $x = 2$ and $y = 1$ is