`A=2+2^2+2^3+..............+2^100`
`A=(2+2^2+2^3+2^4)+..................+(2^97+2^98+2^99+2^100)`
`A=1.(2+2^2+2^3+2^4)+...........................+2^96.(2+2^2+2^3+2^4)`
`A=1.30+....................+2^96. 30`
`A=30.(1+.............+2^96)`
Vì `30vdots5`
`=>30.(1+.............+2^96)vdots5`
`=>Avdots5`