Question

49 x \(\dfrac{1}{2.9}\)+ \(\dfrac{1}{9.16}\)+\(\dfrac{1}{16.23}\)+...............+\(\dfrac{1}{65.72}\):\(\dfrac{1}{3}\) - \(\dfrac{7}{36}\)

Answer 1

Đề là ntn:

\(A=49\left(\dfrac{1}{2.9}+\dfrac{1}{9.16}+\dfrac{1}{16.23}+...+\dfrac{1}{65.72}\right):\dfrac{1}{3}-\dfrac{7}{36}\)

\(A=7\left(\dfrac{1}{2}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{23}+...+\dfrac{1}{65}-\dfrac{1}{72}\right):\dfrac{1}{3}-\dfrac{7}{36}\)

\(A=7\left(\dfrac{1}{2}-\dfrac{1}{72}\right):\dfrac{1}{3}-\dfrac{7}{36}\)

\(A=7.\dfrac{35}{72}:\dfrac{1}{3}-\dfrac{7}{36}\)

\(A=\dfrac{245}{72}:\dfrac{1}{3}-\dfrac{7}{36}\)

\(A=\dfrac{735}{72}-\dfrac{7}{36}=\dfrac{735}{72}-\dfrac{14}{36}=\dfrac{721}{36}\)