Вычислите 1/16*17+1/17*18+1/18*19+1/19*20

Question

Вычислите 1/16*17+1/17*18+1/18*19+1/19*20

Answer 1

1/16*17=1/16-1/17
1/17*18=1/17-1/18 и т.д.
= 1/16-1/17+1/17-1/18+1/18-1/19+1/19-1/20=1/16-1/20=1/80