x-20/11.13-20/13.15-...-20/53.55=3/11
=>x-(20/11.13+20/13.15+...+20/53.55)=3/11
Rồi tính tổng trong ngoặc là OK
ta có: x-\(\left(\frac{20}{11.13}-\frac{20}{13.15}-...-\frac{20}{53.55}\right)=\frac{3}{11}\)
\(x-\left[20\left(\frac{1}{11.13}-\frac{1}{13.15}-...-\frac{1}{53.55}\right)\right]=\frac{3}{11}\)
\(x-\left[20\left(\frac{2}{11.13}-\frac{2}{13.15}-...-\frac{2}{53.55}\right)\right]=\frac{3}{11}\)
\(x-\left[20\left(\frac{1}{11}+\frac{1}{13}-\frac{1}{13}+...-\frac{1}{53}+\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(x-\left[20\left(\frac{1}{11}+\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(x-\left(\frac{20.6}{55}\right)=\frac{3}{11}\)
\(x-\frac{24}{11}=\frac{3}{11}\)
\(x=\frac{3}{11}+\frac{24}{11}\)
\(x=\frac{27}{11}\)
nhóc quậy phá làm sai ồi phải là:
x-[10.(1/11-1/55)]=3/11
x-8/11=3/11
x=1
k nha