Question

B1: Tìm x

a,\(\frac{2}{7}x\)-\(\frac{1}{3}x\) =\(\frac{5}{21}\)

 b, \(\frac{x+1}{1974}\)+ \(\frac{x+2}{1973}\)+ \(\frac{x+3}{1972}\)= (-3)

B2: Tính

\(\frac{-9}{7}\)- \(\frac{5}{13}\)\(\frac{-39}{25}\)+ \(\frac{-1}{42}\)x \(\frac{-5}{6}\)

Mọi người giúp mình với ạ. Mình cảm ơn trước nhé ^_^

Answer 1

a) \(\frac{2}{7}x-\frac{1}{3}x=\frac{5}{21}\)

\(\left(\frac{2}{7}-\frac{1}{3}\right)x=\frac{5}{21}\)

\(\left(-\frac{1}{21}\right)x=\frac{5}{21}\Rightarrow x=\frac{5}{21}:-\frac{1}{21}=-5\)

b) \(\frac{x+1}{1974}+\frac{x+2}{1973}+\frac{x+3}{1972}=-3\)

\(\left(\frac{x+1}{1974}+1\right)+\left(\frac{x+2}{1973}+1\right)+\left(\frac{x+3}{1972}+1\right)=-3+3\)

\(\frac{x+1975}{1974}+\frac{x+1975}{1973}+\frac{x+1975}{1972}=0\)

\(\left(x+1975\right)\left(\frac{1}{1974}+\frac{1}{1973}+\frac{1}{1972}\right)=0\)

Mà \(\frac{1}{1974}+\frac{1}{1973}+\frac{1}{1972}>0\Rightarrow x+1975=0\)

\(x=-1975\)

Answer 2

a) x = - 5

b) x= - 1975