How do you solve the cubic equations like 8x^3+4x^2-4x-1=0 and y^3+4y^2+3y-1=0 withour a calculator?
With some difficulty! See http://en.wikipedia.org/wiki/Cubic_function, for example, for how to do it.
The solution to your first example (done with a calculator!) is shown below. It's a screen shot of part of the Microsoft Mathematics 4 calculator, which is a free download.

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