For any field F, let f(x) = xn + an-1xn-l + ∙∙∙∙∙∙∙∙ + a1x + a0 ∈ F[x]. lf r1,r2, . . ., rn are the roots of f(x), and r1 ∈ F for all 1 < i < n, prove that
(a) -an-i - r1 + r2 + • • • + rn.
b) (-1 )na0 = r1xr2 ∙∙∙∙∙∙ - rn.