2. Let the function $f: \mathbf{R} \rightarrow \mathbf{R}$, for any real number $x$ we have $f\left(x^{2}+x\right)+2 f\left(x^{2}-3 x+2\right)=9 x^{2}-15 x$. Then $f(50)=(\quad$.
(A) 72
(B) 73
(C) 144
(D) 146
Hint: Choose D. Let $x=\frac{\sqrt{201}-1}{2}$ and $x=\frac{3-\sqrt{201}}{2}$.