Question

se considera numărul a=2/3x1+2/3x5+....+2/49x51. Cu cat este egal a

Answer 1

$a= \frac{2}{1*3}+ \frac{2}{3*5}+....+ \frac{2}{49*51}$
$\frac{2}{1*3}=1-\frac{1}{3}$
$\frac{2}{3*5}=\frac{1}{3}-\frac{1}{5}$
.............
$\frac{2}{49*51}=\frac{1}{49}-\frac{1}{51}$
Observam ca se reduc $a=1-\frac{1}{51}=\frac{50}{51}$