Chọn câu đúng nhất

Ta có
${(}\dfrac{1}{2}{a}^{2}{x}^{4}{+}\dfrac{4}{3}{a}{x}^{3}{-}\dfrac{2}{3}{a}{x}^{2}{)}{:}{(}\dfrac{{{-}{2}}}{3}{a}{x}^{2}{)}{=}{(}\dfrac{1}{2}{a}^{2}{x}^{4}{)}{:}{(}\dfrac{{{-}{2}}}{3}{a}{x}^{2}{)}{+}{(}\dfrac{4}{3}{a}{x}^{3}{)}{:}{(}\dfrac{{{-}{2}}}{3}{a}{x}^{2}{)}{-}{(}\dfrac{2}{3}{a}{x}^{2}{)}{:}{(}\dfrac{{{-}{2}}}{3}{a}{x}^{2}{)}{=}\dfrac{{{-}{3}}}{4}{a}{x}^{2}{-}{2}{x}{+}{1}$
Và
${(}\dfrac{1}{2}{a}^{2}{x}^{4}{+}\dfrac{4}{3}{a}{x}^{3}{-}\dfrac{2}{3}{a}{x}^{2}{)}{:}{(}{a}{x}^{2}{)}{=}{(}\dfrac{1}{2}{a}^{2}{x}^{4}{)}{:}{(}{a}{x}^{2}{)}{+}{(}\dfrac{4}{3}{a}{x}^{3}{)}{:}{(}{a}{x}^{2}{)}{-}{(}\dfrac{2}{3}{a}{x}^{2}{)}{:}{(}{a}{x}^{2}{)}{=}\dfrac{1}{2}{a}{x}^{2}{+}\dfrac{4}{3}{x}{-}\dfrac{2}{3}$
Đáp án cần chọn là: C