Question

Tính 1/2 + -1/3 + 1/4 + -1/5 + 1/6 + -1/7 + 1/8 + 1/7 + -1/6 + 1/5 + -1/4 + 1/3 + -1/2

Answer 1

1/2+-1/2+1/3+-1/3+.....+1/7+-1/7+1/8 = 1/8

So doi nhau

tjck cko mjk nka

Answer 2

bằng 1/8

Answer 3

\(\frac{1}{2}+\frac{-1}{3}+\frac{1}{4}+\frac{-1}{5}+\frac{1}{6}+\frac{-1}{7}+\frac{1}{8}+\frac{1}{7}+\frac{-1}{6}+\frac{1}{5}+\frac{-1}{4}+\frac{1}{3}+\frac{-1}{2}\)

= \(\frac{1}{6}\)+ \(\frac{1}{20}\)+ \(\frac{1}{42}\)+ \(\frac{15}{56}\)+ \(\frac{1}{30}\)+ \(\frac{1}{12}\)

= \(\frac{13}{60}\)+ \(\frac{7}{24}\)+ \(\frac{7}{60}\)

= \(\left(\frac{13}{60}+\frac{7}{60}\right)\)+ \(\frac{7}{24}\)

= \(\frac{1}{3}\)+ \(\frac{7}{24}\)

= \(\frac{8}{24}\)+ \(\frac{7}{24}\)

= \(\frac{15}{24}\)

= \(\frac{5}{8}\)

Answer 4

Ta có: \(\frac{1}{2}+\frac{-1}{3}+\frac{1}{4}+\frac{-1}{5}+\frac{1}{6}+\frac{-1}{7}+\frac{1}{7}+\frac{-1}{6}+\frac{1}{5}+\frac{-1}{4}+\frac{1}{3}+\frac{-1}{2}.\)

\(=\left(\frac{1}{2}+\frac{-1}{2}\right)+\left(\frac{1}{3}+\frac{-1}{3}\right)+\left(\frac{1}{4}+\frac{-1}{4}\right)+....+\left(\frac{1}{7}+\frac{-1}{7}\right)+\frac{1}{8}\)

 \(=0+\frac{1}{8}=\frac{1}{8}\)