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 ^_^
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 \(\frac{1}{1974}+\frac{1}{1973}+\frac{1}{1972}>0\Rightarrow x+1975=0\)
\(x=-1975\)
a) x = - 5
b) x= - 1975