4. 若f(x) = 2x + 2x + √2x +,則f(x)為:  (A)2/(2f(x)-1)(B)2/(2f(x)+1)(C)2/(f(x)-1)(D)2/(f(x)+1)

8. 若x siny=y sinx,則 \( \frac{dy}{dx} \)是:(A)\( \frac{2x \sin y + y^2 \cos x}{2y \sin x + x^2 \cos y} \)(B) \( \frac{2x \sin y - y^2 \cos x}{2y \sin x + x^2 \cos y} \)(C)\( \frac{2x \sin y + y^2 \cos x}{2y \sin x - x^2 \cos y} \)(D)\( \frac{2x \sin y - y^2 \cos x}{2y \sin x - x^2 \cos y} \)