Question

2 Tính :

A=\(\dfrac{5}{11×16}\)+\(\dfrac{5}{16×21}\)+\(\dfrac{5}{21×26}\)+...+\(\dfrac{5}{61×66}\)

Answer 1

\(A=\dfrac{5}{11.16}+\dfrac{5}{16.21}+\dfrac{5}{21.26}+...............+\dfrac{5}{61.66}\)

\(\Leftrightarrow A=\dfrac{1}{11}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{21}+\dfrac{1}{21}-\dfrac{1}{26}+............+\dfrac{1}{61}-\dfrac{1}{66}\)

\(\Leftrightarrow A=\dfrac{1}{11}-\dfrac{1}{66}=\dfrac{5}{66}\)

Answer 2

\(A=\dfrac{5}{11\times16}+\dfrac{5}{16\times21}+\dfrac{5}{21\times26}+...+\dfrac{5}{61\times66}\)

\(=\dfrac{1}{11}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{21}+\dfrac{1}{21}-\dfrac{1}{26}+...+\dfrac{1}{61}-\dfrac{1}{66}\)

\(=\dfrac{1}{11}-\dfrac{1}{66}\)

\(=\dfrac{5}{66}\)

~ Học tốt ~

Answer 3

\(A=\dfrac{5}{11.16}+\dfrac{5}{16.21}+\dfrac{5}{21.26}+...+\dfrac{5}{61.66}\)

\(=\left(\dfrac{1}{11}-\dfrac{1}{16}\right)+\left(\dfrac{1}{16}+\dfrac{1}{21}\right)+...+\left(\dfrac{1}{61}+\dfrac{1}{66}\right)\)

\(=\dfrac{1}{11}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{21}+...+\dfrac{1}{61}-\dfrac{1}{66}\)

\(=\dfrac{1}{11}-\dfrac{1}{66}\)

\(=\dfrac{5}{66}\)

Answer 4

\(A=\dfrac{5}{11.16}+\dfrac{5}{16.21}+\dfrac{5}{21.26}+...+\dfrac{5}{61.66}\)

\(A=\dfrac{1}{11}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{21}+\dfrac{1}{21}-\dfrac{1}{26}+...+\dfrac{1}{61}-\dfrac{1}{66}\)

\(A=\dfrac{1}{11}-\dfrac{1}{66}\)

\(A=\dfrac{5}{66}\)

Answer 5

\(=>A=\left(\dfrac{1}{11}-\dfrac{1}{16}\right)+\left(\dfrac{1}{16}-\dfrac{1}{21}\right)+....+\left(\dfrac{1}{61}-\dfrac{1}{66}\right)\)

\(=>A=\dfrac{1}{11}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{21}+......+\dfrac{1}{61}-\dfrac{1}{66}\)

\(=>A=\dfrac{1}{11}-\dfrac{1}{66}=\dfrac{5}{66}\)

CHÚC BẠN HỌC TỐT............

Answer 6

\(A=\dfrac{5}{11.16}+\dfrac{5}{16.21}+\dfrac{5}{21.26}+...+\dfrac{5}{61.66}\)

Theo đề bài ta có:

\(A=\left(\dfrac{1}{11}-\dfrac{1}{16}\right)+\left(\dfrac{1}{16}-\dfrac{1}{21}\right)+...+\left(\dfrac{1}{61}-\dfrac{1}{66}\right)\)

\(A=\left(\dfrac{1}{11}-\dfrac{1}{66}\right)\)

\(A=\dfrac{5}{66}\)

Answer 7

A = \(\dfrac{5}{11.16}+\dfrac{5}{16.21}+\dfrac{5}{21.26}+...+\dfrac{5}{61.66}\)

A = \(\dfrac{1}{11}-\dfrac{1}{16}+\dfrac{1}{16}-\dfrac{1}{21}+\dfrac{1}{21}-\dfrac{1}{26}+...+\dfrac{1}{61}-\dfrac{1}{66}\)

A = \(\dfrac{1}{11}-\dfrac{1}{66}=\dfrac{5}{66}\)