Question

tính giá trị biểu thức : A = 9/1.2+9/2.3+9/3.4+...+9/98.99+9/99.100

Answer 1

\(A=9\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{99}-\dfrac{1}{100}\right)=9\left(1-\dfrac{1}{100}\right)=\dfrac{891}{100}\)