Question

Tính giá trị biểu thức:

P = \(\dfrac{1}{2.5}\)+ \(\dfrac{1}{5.8}\)+ \(\dfrac{1}{8.11}\)+ ... + \(\dfrac{1}{97.100}\)

Làm hộ mình với các bạn

Answer 1

\(P=\dfrac{1}{2\cdot5}+\dfrac{1}{5\cdot8}+\dfrac{1}{8\cdot11}+...+\dfrac{1}{97\cdot100}\)

\(P=\left(\dfrac{1}{2}-\dfrac{1}{5}\right)+\left(\dfrac{1}{5}-\dfrac{1}{8}\right)+...+\left(\dfrac{1}{97}-\dfrac{1}{100}\right)\)

\(P=\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+...+\dfrac{1}{97}-\dfrac{1}{100}\)

\(P=\dfrac{1}{2}-\dfrac{1}{100}\)

\(P=\dfrac{50}{100}-\dfrac{1}{100}\)

\(P=\dfrac{49}{100}\)