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**MathTooHard** I don't think this problem is too difficult, but I have no idea for what it's asking:

For the vector field $\displaystyle \textbf{F}(x,y)=\textbf{i}+x\textbf{j}$, if the parametric flow lines are $\displaystyle x=x(t)$, $\displaystyle y=y(t)$, what differential equations do these functions satisfy? Deduce that $\displaystyle \frac{dy}{dx}=x$.

First off, I don't know what $\displaystyle x=x(t)$ and $\displaystyle y=y(t)$ mean, and how $\displaystyle t$ comes into play. Could someone help?