Răspuns:
Explicație pas cu pas:
[tex]a)~\frac{5+10+15+...+150}{6+12+18+...+180} =\frac{5(1+2+3+...+30)}{6(1+2+3+...+30)}=\frac{5}{6};\\ b) x+y=(\frac{1}{2}+\frac{2}{3} +\frac{3}{4} +\frac{4}{5}+...+\frac{10}{11} )+(\frac{1}{2}+ \frac{1}{3}+\frac{1}{4} +\frac{1}{5} +...+\frac{1}{11} )=(\frac{1}{2}+\frac{1}{2})+(\frac{2}{3} +\frac{1}{3})+(\frac{3}{4}+\frac{1}{4})+(\frac{4}{5}+\frac{1}{5} )+...+(\frac{10}{11} +\frac{1}{11})=1+1+1+1+...+1=1*10=10.[/tex]
