Answer:
[tex]\large\boxed{C.\ \dfrac{-2x^2-x+72}{8x^2}}[/tex]
Step-by-step explanation:
[tex]\dfrac{9}{x^2}-\dfrac{2x+1}{8x}=\dfrac{9\cdot8}{x^2\cdot8}-\dfrac{(2x+1)\cdot x}{8x\cdot x}\qquad\text{use the distributive property}\\\\=\dfrac{72}{8x^2}-\dfrac{2x^2+x}{8x^2}=\dfrac{72-(2x^2+x)}{8x^2}=\dfrac{72-2x^2-x}{8x^2}\\\\=\dfrac{-2x^2-x+72}{8x^2}[/tex]
