1+1(1+x)+1(1+x)(1+x+10%)=3.31
2+x+(1+x)(1.1+x)=2+x+1.1+2.1x+x^2=x^2+3.1x+3.1=3.31
x^2+3.1x-0.21=0 x=6.6%
1+1(1+x)+1(1+x)^2+…+(1+x)^n=(1-x^n)/(1-x)
1+1(1+x)+1(1+x)(1+x+10%)=3.31
2+x+(1+x)(1.1+x)=2+x+1.1+2.1x+x^2=x^2+3.1x+3.1=3.31
x^2+3.1x-0.21=0 x=6.6%
1+1(1+x)+1(1+x)^2+…+(1+x)^n=(1-x^n)/(1-x)