làm tiếp cái trước(ấn nhầm)
\(x=\frac{5}{42}-\frac{15}{28}\)
\(x=\frac{5.4}{6.4.7}-\frac{15.6}{4.7.6}\)
\(x=\frac{20}{168}-\frac{90}{168}\)
\(x=\frac{-70}{168}\)
\(x=\frac{-5}{12}\)
2.
1.
\(\frac{11}{13}-\left(\frac{5}{42}-x\right)=-\left(\frac{15}{28}-\frac{11}{13}\right)\)
\(\frac{11}{13}-\frac{5}{42}+x=-\frac{15}{28}+\frac{11}{13}\)
\(\frac{11}{13}-\frac{11}{13}-\frac{5}{42}+\frac{15}{28}=-x\)
/x+\(\frac{4}{15}\)/ \(-\)\(3,75\)\(=\)\(-2,15\)
/ \(x+\frac{4}{15}\)/ \(=\)\(-2,15+3,75\)
/ \(x+\frac{4}{15}\)/ \(=\)\(\frac{8}{5}\)
TH1: \(x+\frac{4}{15}=\frac{8}{5}\) TH2: \(x+\frac{4}{15}=-\frac{8}{5}\)
\(=>x=\frac{8}{5}-\frac{4}{15}\) \(=>x=-\frac{8}{5}-\frac{4}{15}\)
\(=>x=\frac{24}{15}-\frac{4}{15}\) \(=>x=-\frac{24}{15}-\frac{4}{15}\)
\(=>x=\frac{20}{15}\) \(=>x=-\frac{28}{15}\)
\(=>x=\frac{4}{3}\)
3. /\(4.x\)/ \(-\)\(13,5\)\(=\)\(\frac{9}{4}\)
/ \(4.x\)/ \(=\frac{9}{4}+\frac{27}{2}\)
/ \(4.x\)/ \(=\frac{9}{4}+\frac{54}{4}\)
/ \(4.x\)/ \(=\frac{63}{4}\)
TH1: \(4.x=\frac{63}{4}\) TH2: \(4.x=-\frac{63}{4}\)
\(x=\frac{63}{16}\) \(x=-\frac{63}{16}\)
vậy \(x=\frac{63}{16}\)hoặc \(x=\frac{-63}{16}\)