Question

S=1/2.4+1/4.6+1/6.8+1/8.10 tính  S

 

Answer 1

\(S=\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+\frac{1}{8.10}\)

\(S=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}\)

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

\(S=\frac{2}{5}\)

Answer 2

S = 1 / 2.4 + 1/ 4.6 + 1 / 6.8 + 1 / 8.10

2S = 2 / 2.4 + 2 / 4.6 + 2/ 6.8 + 2 / 8.10

2S = 1 2 - 1 / 4 + 1 / 4 - 1 / 6 + 1 / 6 - 1 / 8 + 1 / 8 - 1 / 10

2S = 1 / 2 - 1 / 10

2S = 2 / 5 

  S = 2 / 5 : 2

  S = 1 / 5