a) \(D=x+\left|x\right|\)
Nếu \(x\ge0\)thì: \(D=x+x=2x\)Nếu \(x< 0\) thì: \(D=x-x=0\)b) \(E=\left|x-7\right|+6-x\)
Nếu \(x\ge7\)thì: \(E=x-7+6-x=-1\)Nếu \(x< 7\)thì: \(E=7-x+6-x=13-2x\)c) \(C=x+\frac{1}{2}-\left|x-\frac{2}{3}\right|\)
Nếu \(x\ge\frac{2}{3}\)thì: \(C=x+\frac{1}{2}-\left(x-\frac{2}{3}\right)=x+\frac{1}{2}-x+\frac{2}{3}==\frac{7}{6}\)Nếu \(x< \frac{2}{3}\)thì: \(C=x+\frac{1}{2}-\left(\frac{2}{3}-x\right)=x+\frac{1}{2}-\frac{2}{3}+x=2x-\frac{1}{6}\)