Đáp án:
Giải thích các bước giải:
`A=100/1*101+100/2*102+...+100/24*124+100/25*125`
`A=100/1.101+100/2.102+...+100/24.124+100/25.125`
`A=1/1- 1/101+ 1/2 - 1/102 +..+ 1/24 -1/124 + 1/25- 1/125`
`A=(1/1+ 1/2 +...+ 1/24+ 1/25)-(1/101 + 1/102 +...+ 1/124 + 1/125)`
`A=(1/1+ 1/2 +...+ 1/24+ 1/25+..+1/99+1/100)-(1/26 + 1/27 +...+ 1/124 + 1/125)`
Lại có:
`B=25/1*26+25/2*27+...+25/99*124+ 25/100*125`
`B=25/1.26+25/2.27+...+25/99.124+25/100.125`
`B=1/1 - 1/26 + 1/2 - 1/27 +..+ 1/99- 1/124+ 1/100 - 1/125`
`B=(1/1+ 1/2 +...+ 1/99+ 1/100)-(1/26 + 1/27 +...+ 1/124 + 1/125)`
`=>A=B(đpcm)`
