c)
\(\left|3x-4\right|+4=3x\\ \left|3x-4\right|=3x-4\\ \left|3x-4\right|^2=\left(3x-4\right)^2\\ \left(3x-4\right)^2-\left(3x-4\right)^2=0\\ 0=0\\ \Rightarrow pt\: vô\: số\: nghiệm\)
d)
\(\left|7-2x\right|+7=2x\\ \left|2x-7\right|=2x-7\\ 0=0\left(tương\:tự\:câu\:c\right)\\ \Rightarrow pt\:vô\:số\:nghiệm\)