(2x−32x3)=?(a) 2(x−4)(x+4)(b) 2x(1−2x)2(c) 2x(1+2x)2(d) 2x(1−4x)(1+4x)
Sum to n terms of the series 1(1+x)(1+2x) + 1(1+2x)(1+3x) + 1(1+3x)(1+4x) + ..............is