If a−b=4,a2+b2+ab=8,thena3−b3=?
If a3+b3=27 and a2+b2−ab=9, then a+b=___
If x = 1 + a + a2 .......... to ∞ (|a|<1), y = 1 + b + b2 ......... to ∞ (|b| < 1), then Z = 1 + ab + a2 b2 + a3 b3..... to ∞ is