2/3*5+2/5*7+2/7*9+2/9*11+...+2/99*101
=2/3*3+2/5*5+2/7*7+2/9*9+...+2/99*99+2x2x(1/3+1/5+1/7+1/9+...+1/99)
=2x49+4x[(2-1)/(1+2)+(3-2)/(3+2)``````)
=98+1-1/50
=99-1/50
=98又49/50
有不懂再问,
2/3*5+2/5*7+2/7*9+2/9*11+...+2/99*101
=2/3*3+2/5*5+2/7*7+2/9*9+...+2/99*99+2x2x(1/3+1/5+1/7+1/9+...+1/99)
=2x49+4x[(2-1)/(1+2)+(3-2)/(3+2)``````)
=98+1-1/50
=99-1/50
=98又49/50
有不懂再问,