Question

Tìm phân số \(\dfrac{a}{b}\)

a) \(\dfrac{1}{2}+\dfrac{a}{b}-\dfrac{1}{4}\) = \(\dfrac{21}{20}\)              

b)\(\dfrac{a}{b}\) x \(\dfrac{3}{4}+\dfrac{1}{6}\) = \(\dfrac{5}{12}\)

giúp vs mn uiii. đúng nhé

Answer 1

\(a)\dfrac{1}{2} +\dfrac{a}{b}-\dfrac{1}{4}=\dfrac{21}{20}=> \dfrac{1}{2}+\dfrac{a}{b}=\dfrac{21}{20}+\dfrac{1}{4} =>\dfrac{1}{2}+\dfrac{a}{b}=\dfrac{26}{20} =>\dfrac{a}{b}=\dfrac{26}{20}-\dfrac{1}{2} =>\dfrac{16}{20}=\dfrac{4}{5}\)

Answer 2

b) \(\dfrac{a}{b}.\dfrac{3}{4}+\dfrac{1}{6}=\dfrac{5}{12}=>\dfrac{a}{b}.\dfrac{3}{4}=\dfrac{5}{12}-\dfrac{1}{6}=>\dfrac{a}{b}.\dfrac{3}{7}=\dfrac{7}{12}=>\dfrac{a}{b}=\dfrac{7}{12}:\dfrac{3}{4}=>\dfrac{a}{b}=\dfrac{28}{36}=\dfrac{7}{9}\)