Question

Aratati ca
a. $\frac{3}{4} \ \textless \ \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{1}{6} + \frac{1}{7} + \frac{1}{8} \ \textless \ 2$
b.$\frac{2}{3} \ \textless \ \frac{1}{10} + \frac{1}{11} +...+ \frac{1}{27} \ \textless \ \frac{9}{5}$

Answer 1

a)3/4<1/3+1/4+1/5+1/6+1/7 +1/8 <2
=3/4 <1/33<2
=3/4<1/33 A (adevarat)
=1/33<2 A(adevarat )

b )2/3<1/10+1/11+...+1/27<9/5
2/3 <1/10+1/11+1/12+1/13+1/14+1/15 +1/16 +1/17 +1/18 +1/19+1/20+1/21+1/22+1/23+1/24+1/25+1/26+1/27
=2/3 <1/333<9/5
ps=nu sunt sigura daca e bine ,mai verifica !