a: \(\Leftrightarrow6x^2-2x=6x^2-13\)
=>-2x=-13
hay x=13/2
b: \(\dfrac{x}{3}-\dfrac{2x+1}{6}=\dfrac{x}{6}-x\)
=>2x-2x-1=x-6x
=>-5x=-1
hay x=1/5
c: \(\Leftrightarrow\left(x+1\right)^2-\left(x-1\right)^2=x^2+3\)
\(\Leftrightarrow x^2+3-x^2-2x-1+x^2-2x-1=0\)
\(\Leftrightarrow\left(x-1\right)\left(x-3\right)=0\)
=>x=3