Bài 20
b) Ta có
$VT = \dfrac{\overline{a00a}}{\overline{b00b}} = \dfrac{a . 1001}{b.1001} = \dfrac{a}{b} = VP$
c) Ta có
$VT = \dfrac{\overline{ab00ab}}{\overline{cd00cd}} = \dfrac{\overline{ab}.10001}{\overline{cd} . 10001} = \dfrac{\overline{ab}}{\overline{cd}} = VP$.