Question

cmr 1-\(\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+.......-\frac{1}{1990}=\frac{1}{996}+\frac{1}{997}+\frac{1}{998}+.......+\frac{1}{1990}\)

Answer 1

xét vế trái

=(1+1/3+1/5+...+1/1989)-(1/2+1/4+...+1/1990)

=(1+1/2+1/3+1/4+...+1/1990)-2.(1/2+1/4+...+1/1990)

=(1+1/2+1/3+1/4+...+1/1990)-!1+1/2+1/3+1/4+...+1/995)

=1/996+1/997+.../1+1990

vậy 1-1/2+1/3-1/4+...-1/1990=1/996+1/997+...+1/1990

Answer 2

cmr 1-$\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+.......-\frac{1}{1990}=\frac{1}{996}+\frac{1}{997}+\frac{1}{998}+.......+\frac{1}{1990}$

Answer 3

dòng dấu = thứ 3 sửa ! thành ( nha