a: \(\Leftrightarrow x\cdot\left(0.35+\dfrac{3}{4}\right)=\dfrac{4+x}{10}+\dfrac{10x-390}{10}\)
\(\Leftrightarrow\dfrac{11x}{10}=\dfrac{11x-386}{10}\)
=>11x=11x-386(vô lý)
b: \(\Leftrightarrow x^3+3x^2+3x+1+1-3x^2+3x-x^3-6x^2-6x=6\)
\(\Leftrightarrow-6x^2+2=6\)
\(\Leftrightarrow-6x^2=4\)(vô lý)