4. Give the form of the partial fraction decomposition for x4 - 1 A B C (a) + x- 1 x+1 x2 +1 A B Cx (b) x2 + 1 A B Ca + D (c) x-1 x2 +1 A B (d) + x2 - 1 x2 + 1 (e) none of these