\( \displaystyle{{ - 1} \over 2} = {3 \over { - 6}}\) vì \( \displaystyle-1.(-6) = 3.2 = 6\)
\( \displaystyle{{ - 4} \over 8} = {1 \over { - 2}}\) vì \( \displaystyle-4.(-2) = 1.8 = 8\)
\( \displaystyle{5 \over { - 10}} = {{ - 1} \over 2}\) vì \( \displaystyle5.2 = -1.(-10) = 10\)