Question

1/2x3 +1/3x4 + 1/4x5 +....+ 1/9x10

có lời giải nhé

Answer 1

1/2.3+1/3.4+...+1/9.10

=1/2-1/3+1/3-1/4+1/4-1/5+...+1/9-1/10

=1/2-1/10=2/5

Answer 2

Ta có : \(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+......+\frac{1}{9.10}\)

\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+.......+\frac{1}{10}\)

\(=\frac{1}{2}-\frac{1}{10}=\frac{5}{10}-\frac{1}{10}=\frac{2}{5}\)