Question

 \(\frac{1}{3.4}\) + \(\frac{1}{4.5}\)​​+ \(\frac{1}{5.6}\)+ \(\frac{1}{6.7}\)+...........+ \(\frac{1}{49.50}\)

dấu chấm ở số thập phân là nhân

Answer 1

\(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+........+\frac{1}{49.50}\)

=\(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+......+\frac{1}{49}-\frac{1}{50}\)

=\(1-\frac{1}{50}\)

=\(\frac{49}{50}\)

Answer 2

      \(\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+...+\frac{1}{49\times50}\)

\(=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)

\(=1-\frac{1}{50}\)

\(=\frac{49}{50}.\)

Answer 3

\(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{49.50}\)

\(=\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}\right)\)

\(=1-\frac{1}{50}\)

\(=\frac{49}{50}\)

Answer 4

=1-1/2+1/2-1/3+1/3-...-1/50

=1-1/50

=49/50