\(A=\dfrac{1^2}{1.2}.\dfrac{2^2}{2.3}.\dfrac{3^2}{3.4}.\dfrac{4^2}{4.5}.\dfrac{5^2}{5.6}\\ =\dfrac{1.1}{1.2}.\dfrac{2.2}{2.3}.\dfrac{3.3}{3.4}.\dfrac{4.4}{4.5}.\dfrac{5.5}{5.6}\\ =\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}.\dfrac{4}{5}.\dfrac{5}{6}\\ =\dfrac{1}{6}\)
\(A=\dfrac{1^2}{1.2}\times\dfrac{2^2}{2.3}\times\dfrac{3^2}{3.4}\times\dfrac{4^2}{4.5}\times\dfrac{5^2}{5.6}\\ A=\dfrac{1.2.3.4.5}{1.2.3.4.5}\times\dfrac{1.2.3.4.5}{2.3.4.5.6}\\ A=1\times\dfrac{1}{6}=\dfrac{1}{6}\)
Ta có :
\(A=\dfrac{1^2}{1.2}.\dfrac{2^2}{2.3}.\dfrac{3^2}{3.4}.\dfrac{4^2}{4.5}.\dfrac{5^2}{5.6}\)\(=\dfrac{1.1.2.2.3.3.4.4.5.5}{1.2.2.3.3.4.4.5.5.6}\)
\(=\dfrac{1.2.3.4.5}{1.2.3.4.5}.\dfrac{1.2.3.4.5}{2.3.4.5.6}=1.\dfrac{1}{6}=\dfrac{1}{6}\)
Ko hiểu chỗ nào hỏi mình nha
