`11E = 11^2 + 11^3 + ... + 11^101`
`11E - E = (11^2+ ... + 11^101) - (11 + 11^2 + ... + 11^100)`
`10E = 11^101 - 11`
`E = (11^101-11)/10`
\(11E=11^2+11^3+...+11^{101}\Rightarrow10E-E=-11+11^{101}\Leftrightarrow E=\dfrac{-11+11^{101}}{9}\)
sửa \(11E-E=-11+11^{101}\Rightarrow E=\dfrac{-11+11^{101}}{10}\)