I'm trying to do my prelab for an E&M course, and am asked if, for plotting $V$ vs $I$ with a varying temperature, I should expect a linear slope. I know that both $V$ and $I$ depend on $R$, and since $R$ is proportional to $T$ that I shouldn't.

Trying to show this, I'm having some problems -- probably because my differential equations skills are a bit rusty.

Simplely, if $V = I \,R(T)$, how do I take $\mathrm{d}V/\mathrm{d}I$?

I can find $\mathrm{d}V/\mathrm{d}T$ by chain rule, but i'm just drawing a blank with $\mathrm{d}V/\mathrm{d}I$ since $I = V/R(T)$

Excuse my ineptitude, and thanks in advanced for helping me out.