I am in my final semester graduating from a liberal arts college (physics/math major) and intend to study high-energy theory in graduate school. Coming from a smaller college I have not had the opportunity to take courses in partial differential equations, integral equations, or numerical/computational methods.  What resources, in the aforementioned fields, might one recommend to a student looking to get sufficiently up to speed for graduate level coursework and research (n.b. I do solid math background, in general, including linear algebra and complex analysis, which might come in handy for such topis/learning)?
In his first lesson (transcripted in "Tips on Physics"), Feynman talks about math for physicists in a very cool and practical way. And at the end of the section he talks something like "so the first thing to do is to learn to learn derivative, integral and algebra" (I don't know how much precise I'm being because I've read it in Portuguese). I would to know if there is some book that deals with math as Feynman did it in this lesson (respecting formalities, but teaching how to use the practical rules)? Also, someone have any recommendations for algebra book (college level)?
I'd prefer as little formal definition as possible and simple mathematics.