In each of Problems 9 through 20:
(a) Find the solution of the given initial value problem in explicit form.
(b) Plot the graph of the solution.
(c) Determine (at least approximately) the interval in which the solution is defined.
9. $y' = (1 - 2x)y^2$, $y(0) = -1/6$
10. $y' = (1 - 2x)/y$, $y(1) = -2$
11. $x dx + ye^{-x} dy = 0$, $y(0) = 1$
12. $dr/d\theta = r^2/\theta$, $r(1) = 2$
13. $y' = 2x/(y + x^2y)$, $y(0) = -2$
14. $y' = xy^3(1 + x^2)^{-1/2}$, $y(0) = 1$
15. $y' = 2x/(1 + 2y)$, $y(2) = 0$
16. $y' = x(x^2 + 1)/4y^3$, $y(0) = -1/\sqrt{2}$
