Question

tim x : \(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{47.49}=\frac{1}{x}\)

Answer 1

=1-1/3+1/3-1/5+.....+1/47-1/49

=1-1/49

=)x=49

...kcho minh nha

Answer 2

\(\frac{1}{1.3}+\frac{1}{3.5}+...+\frac{1}{47.49}=\frac{1}{x}\)

\(\frac{1}{2}\left(\frac{2}{1.3}+\frac{2}{3.5}+...+\frac{2}{47.49}\right)=\frac{1}{x}\)

\(\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{37}-\frac{1}{49}\right)=\frac{1}{x}\)

\(\frac{1}{2}\left(1-\frac{1}{49}\right)=\frac{1}{x}\)

\(\frac{1}{2}\cdot\frac{48}{49}=\frac{1}{x}\)

\(\frac{1}{x}=\frac{24}{49}\)

=>x=49/24