## tanvirzawad 4 years ago prove that, r^m + r^(m+1) + ... + r^(n-1) + r^n = (r^(n+1)-r^m)/(r-1)

1. anonymous

its a geometric progression(GP). GP has a formula $a+a*r+a*r ^{2}+ a*r ^{3}+....+a*r ^{n-1}=a*\left( r ^{n} - 1 \right)/(r-1)$

2. anonymous

for prove of GP you can search on google