b, \(\Rightarrow14x-7-15x-6=21\left(x+13\right)\)
\(\Leftrightarrow-x-13=21x+273\Leftrightarrow-22x=286\Leftrightarrow x=-13\)
c, đk : x khác 2 ; -2
\(\Rightarrow x^2-3x+2-x^2-2x=6-7x\Leftrightarrow-5x+2=6-7x\)
\(\Leftrightarrow2x=4\Leftrightarrow x=2\)(ktm)
pt vô nghiệm