Bài này khó quá!!!
\(\dfrac{\dfrac{2}{3}-\dfrac{2}{5}+\dfrac{2}{9}+\dfrac{2}{13}}{\dfrac{11}{3}-\dfrac{11}{5}+\dfrac{11}{9}+\dfrac{11}{13}}\)
\(=\dfrac{2\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{13}\right)}{11\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{13}\right)}\)
\(=\dfrac{2}{11}\)
Ta có:
\(\dfrac{\dfrac{2}{3}-\dfrac{2}{5}+\dfrac{2}{9}+\dfrac{2}{13}}{\dfrac{11}{3}-\dfrac{11}{5}+\dfrac{11}{9}+\dfrac{11}{3}}\)
\(=\dfrac{2\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{13}\right)}{11\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{3}\right)}\) Rút gọn \(\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{13}\right)\) ở cả tử và mẫu ta được:
\(=\dfrac{2}{11}\)
\(\dfrac{2.\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{13}\right)}{11.\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{9}+\dfrac{1}{13}\right)}\)
\(=\dfrac{1}{11}\)
Chúc bạn học giỏi
