If alpha and beta are the roots of a quadratic equation find the value of alpha^-2 + beta^-2?
If [math]\alpha[/math] and [math]\beta[/math] are two roots of [math]ax^2 + bx + c = 0[/math] then how could I find [math]\frac{1}{\alpha} -\frac{1}{\beta}[/math]?