Question

Tính giá trị biểu thức sau bằng cách hợp lí:

\(\dfrac{\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{9}}{2+\dfrac{6}{5}-\dfrac{2}{3}}\)

Answer 1

\(\dfrac{2.\left(\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}\right)}{2.\left(1+\dfrac{3}{5}-\dfrac{1}{3}\right)}\)

=\(\dfrac{\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}}{1+\dfrac{3}{5}-\dfrac{1}{3}}=\dfrac{\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}}{3.\dfrac{1}{3}+3.\dfrac{1}{5}-3.\dfrac{1}{9}}=\dfrac{\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}}{3.\left(\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}\right)}\)

=\(\dfrac{1}{3}\)

Answer 2

Nhường cho t câu này!!!

\(\dfrac{\dfrac{2}{3}+\dfrac{2}{5}-\dfrac{2}{9}}{2+\dfrac{6}{5}-\dfrac{2}{3}}\)

\(=\dfrac{2\left(\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}\right)}{2\left(1+\dfrac{3}{5}-\dfrac{1}{3}\right)}\)

\(=\dfrac{\dfrac{1}{3}+\dfrac{1}{5}-\dfrac{1}{9}}{1+\dfrac{3}{5}-\dfrac{1}{3}}=\dfrac{1}{3}\)