原式=1/(1x4)+1/(4x7)+1/(7x10)……+1/(97x100)《分母拆开》
=1/3x【(1-1/4)+(1/4-1/7)+(1/7-1/10)+……+(1/97-1/100)】《分母由乘变减,注意乘1/3》
=1/3x(1-1/100)《消去》
=33/100
原式=1/(1x4)+1/(4x7)+1/(7x10)……+1/(97x100)《分母拆开》
=1/3x【(1-1/4)+(1/4-1/7)+(1/7-1/10)+……+(1/97-1/100)】《分母由乘变减,注意乘1/3》
=1/3x(1-1/100)《消去》
=33/100