a: \(\Leftrightarrow\left(3x+1\right)^2-2\left(3x+1\right)\left(3x+5\right)+\left(3x+5\right)^2=4\)
\(\Leftrightarrow\left(3x+1-3x-5\right)^2=4\)
=>16=4(vô lý)
c: \(\Leftrightarrow6x^2+27x+4x+18-6x^2-x-12x-2=x+1-x+6=7\)
=>18x+16=7
=>18x=-9
hay x=-1/2