Выразите b через a если 4/5+6/7+8/9+10/11=a 1/5+1/7+1/9+1/11=b
Найдем а+b=4/5 +6/7+8/9+10/11+1/5+1/7+1/9+1/11=4/5+1/5+6/7+1/7++8/9+1/9+10/11+1/11=1+1+1+1=4a+b=4⇒b=4-a