Đặt \(\displaystyle y = f\left( x \right) = {8 \over x}\).Ta có:
\(\displaystyle f\left( 2 \right) = {8 \over 2} = 4\);
\(\displaystyle f\left( 4 \right) = {8 \over 4} = 2\);
\(\displaystyle f\left( { - 1} \right) = {8 \over { - 1}} = - 8\);
\(\displaystyle f\left( { - 4} \right) = {8 \over { - 4}} = - 2\).
