Question

Calculati
1/1$\frac{1}{1*2}+ \frac{1}{2*3}+.....+\frac{1}{9*10}$

Answer 1

Răspuns:

1/1×2+1/2×3+...+1/9×10=1/1+1/2-1/2+1/3+...+1/9-1/10

reducem fractiile : 1/2 , 1/3 si 1/9

1/1-1/10=

amplificam fractia 1/1 cu 10

10/10-1/10=9/10