Chapter 1 - First-Order Differential Equations - 1.4 Separable Differential Equations - Problems - Page 43: 1

$ln|y|=x^2+C$

Multiply both sides of the equation by $\frac{dx}{y}$. $$(\frac{dx}{y})(\frac{dy}{dx}=2xy)$$ $$\frac{dy}{y}=2xdx$$ Since each side is in terms of one variable, you can integrate. $$\int \frac{dy}{y}=\int 2x dx$$ $$ln|y|=x^2+C$$