If A(1, 2, 3), B(-1, -1, -1) be the points, then the distance AB is [MP PET 2001; Pb. CET 2001]
x=1+a+a2+...∞(a<1) y=1+b+b2+...∞(b<1) Then the value of 1+ab+a2b2+.....∞ is [MNR 1980; MP PET 1985]
[MNR 1980; Pb. CET 1990; DCE 2001]