Răspuns:
Succes!
Explicație pas cu pas:
5) Se simplifica prin 5, atat numitorul cat si numaratorul, adica ii impartim pe rand la 5
5/10=1/2; 25/15=5/3; 115/85=23/17; 5n/55=n/11;
20n/10n+5= 4n/2n+1
6) 2n/2n+1= n€N
n=1=> 2n/2n+1=2×1/2×1+1=2/3
n=2=> 2n/2n+1=2×2/2×2+1=4/5
n=3=> 2n/2n+1=2×3/2×3+1=6/7
n=4=> 2n/2n+1=2×4/2×4+1=8/9
n=5=> 2n/2n+1=2×5/2×5+1=10/11
oricare ar fi n, fractia este ireductibila pt ca numitorul va fi intotdeauna un nr impar.
7) 17/31-11/31+25/31= (17-11+25)/31=31/31=1
