KöMaL 2010 C1038

Define the function $\mathop{\rm lac} (x)$ on the set of real numbers as follows: $\mathop{\rm lac} (x)=x, {\rm if \ } x\in [2n; 2n+1], { \rm \ where \ } n\in\mathbb{Z}, {\rm or} -x+4n+3, {\rm if \ } x\in ]2n+1; 2n+2[, {\rm \ where \ } n\in\mathbb{Z}.$ Solve the equation $\mathop{\rm lac} (2x^2 + x + 4)=\mathop{\rm lac} (x^2 + 7x -1)$ on the set of real numbers.