Question

1/1x2+2/2x4+3/4x7+4/7x11+...+11/56x67

Answer 1

\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+...+\dfrac{1}{56}-\dfrac{1}{67}\)

\(=1-\dfrac{1}{67}=\dfrac{66}{67}\)

Answer 2

Từng câu hay toán bình dương zậy

Answer 3

\(\dfrac{1}{1\times2}+\dfrac{2}{2\times4}+\dfrac{3}{4\times7}+\dfrac{4}{7\times11}+....+\dfrac{11}{56\times67}\)

\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{11}+....+\dfrac{1}{56}-\dfrac{1}{67}\)

\(=1-\dfrac{1}{67}\)

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