4分之1+28分之1+70分之1+130分之1 简便运算

1/4 1/28 1/70 1/130 1/208 =1/(1*4) 1/(4*7) 1/(7*10) 1/(10*13) 1/(13*16) =1/3*[(1/1-1/4) (1/4-1/7) (1/7-

1/4+1/28+1/70+1/130=8/28+1/70+1/130=2/7+1/70+1/130=21/70+1/130=3/10+1/130=40/130=4/13

我也在找

1/4+1/28+1/70+1/130
=1/3(1-1/4)+1/3(1/4-1/7)+1/3(1/7-1/10)+1/3(1/10-1/13)
=1/3(1-1/4+1/4-1/7+1/7-1/10+1/10-1/13)
=1/3(1-1/13)
=1/3*12/13
=4/13

4分之1+28分之1+70分之1+130分之1
=(70+10+4)/280+1/130
=84/280+1/130
=21/70+1/130
=273/910+7/910
=280/910
=4/13

4分之1+28分之1+70分之1+130分之1
=（7+1）28+70分之1+130分之1
=28分之8+70分之1+130分之1
=7分之2+70分之1+130分之1
=（20+1）/70+1/130
=21/70+1/130
=3/10+1/130
=39/130+1/130
=40/130
=4/13