注意到分母的差都是4
先求:
4*(1/1*5+1/5*9+1/9*13+...+1/37*41)
=4/1*5+4/5*9+4/9*13+...+4/37*41
=1/1-1/5+1/5-1/9+1/9-1/13+.+1/37-1/41
=1-1/41
=40/40
∴ 1/1*5+1/5*9+1/9*13+...+1/37*41=10/41
注意到分母的差都是4
先求:
4*(1/1*5+1/5*9+1/9*13+...+1/37*41)
=4/1*5+4/5*9+4/9*13+...+4/37*41
=1/1-1/5+1/5-1/9+1/9-1/13+.+1/37-1/41
=1-1/41
=40/40
∴ 1/1*5+1/5*9+1/9*13+...+1/37*41=10/41