Cho hai số hữu tỉ \(x=a;y=\dfrac{b}{2c}\left(a,b,c\in Z;c\ne0\right)\). Hiệu \(x-y\) bằng
\(\dfrac{a+2bc}{2c}.\)\(\dfrac{a-2bc}{2c}.\)\(\dfrac{2ac+b}{2c}.\)\(\dfrac{2ac-b}{2c}.\)Hướng dẫn giải:Ta có \(x-y=a-\dfrac{b}{2c}=\dfrac{2ac}{2c}-\dfrac{b}{2c}=\dfrac{2ac-b}{2c}.\)
