Câu 2 :
\(a,\dfrac{3}{7}+\dfrac{-10}{7}=1\) b) ko rõ
\(c,\dfrac{-4}{2}:\dfrac{4}{5}=\dfrac{-4}{2}\times\dfrac{5}{4}=\dfrac{-1}{2}\times5=\dfrac{-5}{2}\)
\(d,\dfrac{3}{9}-\dfrac{3}{5}=\dfrac{15}{45}-\dfrac{27}{45}=\left(-\dfrac{8}{45}\right)\)
Câu 3:
\(x-\dfrac{2}{3}=\dfrac{7}{3}\) \(\dfrac{3}{5}+3x=1,25\)
\(x=\dfrac{7}{3}+\dfrac{2}{3}\) \(3x=\dfrac{5}{4}-\dfrac{3}{5}\)
\(x=3\) \(3x=\dfrac{25}{20}-\dfrac{12}{20}\)
\(3x=\dfrac{13}{20}\)
\(x=\dfrac{13}{20}:3\)
\(x=\dfrac{13}{60}\)
Câu 3 :
\(A=\dfrac{12}{9}+\dfrac{-2}{11}+\dfrac{2}{9}+\dfrac{-9}{11}+\dfrac{4}{9}\)
\(A=\left(\dfrac{12}{9}+\dfrac{2}{9}+\dfrac{4}{9}\right)+\left(\dfrac{-2}{11}+\dfrac{-9}{11}\right)\)
\(A=\dfrac{16}{9}+-1\)
\(A=\dfrac{7}{9}\)
\(B=\dfrac{5}{8}.\dfrac{2}{11}+\dfrac{5}{8}.\dfrac{9}{11}+\dfrac{1}{4}\)
\(B=\dfrac{5}{8}.\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+\dfrac{1}{4}\)
\(B=\dfrac{5}{8}+\dfrac{1}{4}\)
\(B=\dfrac{5}{8}+\dfrac{2}{8}\)
\(B=\dfrac{7}{8}\)
