1) \(\dfrac{a}{b}\) = \(\dfrac{x}{y}\) khi nào???

2) Tìm x ∈ Q, biết a) \(\dfrac{x}{12}\) = \(\dfrac{-1}{4}\)

b) \(\dfrac{1}{3}\)^2x-1 = \(\dfrac{1}{243}\)

c) \(\dfrac{4}{7}\).x -\(\dfrac{2}{3}\)= \(\dfrac{1}{5}\)

3) so sánh 5²⁰² và 2⁵⁰⁵