小学数学题，又谁会呢？一，2/2×4+
一，2/2×4+2/4×6+2/6×8+……+2/96×98+2/98×100
(因为每一项的分母为两个数字的乘积，将它们转化为两个分式的差)
=[(1/2)-(1/4)]+[(1/4)-(1/6)]+[(1/6)-(1/8)]+……+[(1/96)-(1/98)]+[(1/98)-(1/100)]
=(1/2)-(1/4)+(1/4)-(1/6)+(1/6)-(1/8)+……+(1/96)-(1/98)+(1/98)-(1/100)
=(1/2)-(1/100)
=49/100
二，1/1×4+1/4×7+1/7×10+1/10×13+1/13×16+1/16×19+1/19×22
=(...全部
一，2/2×4+2/4×6+2/6×8+……+2/96×98+2/98×100
(因为每一项的分母为两个数字的乘积，将它们转化为两个分式的差)
=[(1/2)-(1/4)]+[(1/4)-(1/6)]+[(1/6)-(1/8)]+……+[(1/96)-(1/98)]+[(1/98)-(1/100)]
=(1/2)-(1/4)+(1/4)-(1/6)+(1/6)-(1/8)+……+(1/96)-(1/98)+(1/98)-(1/100)
=(1/2)-(1/100)
=49/100
二，1/1×4+1/4×7+1/7×10+1/10×13+1/13×16+1/16×19+1/19×22
=(1/3)*[1-(1/4)]+(1/3)*[(1/4)-(1/7)]+……+(1/3)*[(1/16)-(1/19)]+(1/3)*[(1/19)-(1/22)]
=(1/3)*[1-(1/4)+(1/4)-(1/7)+……+(1/16)-(1/19)+(1/19)-(1/22)]
=(1/3)*[1-(1/22)]
=(1/3)*(21/22)
=7/22。
收起
