9.設在不等式cases 2x+3y 12 \ 2x+y 8 \ x 0, y 0 cases的條件下，則函數f(x,y)=4x+3y的最小值為何？(A)12(B)16(C)18(D)24

12.設\( f(x) = 3^x \), \( g(x) = \log_{\frac{1}{3}} x \)，則下列選項何者正確？(A)若x1<x2，則\( 3^{x_1} > 3^{x_2} \)(B)若x1<x2，則\( 3^{x_1} + 3^{x_2} = 3^{x_1+x_2} \)(C)若x1<x2，則\( \log_{\frac{1}{3}}(x_2 - x_1) = \log_{\frac{1}{3}} x_2 - \log_{\frac{1}{3}} x_1 \)(D)若x1<x2，則\( \frac{\log_{\frac{1}{3}} x_2 - \log_{\frac{1}{3}} x_1}{x_2 - x_1} < 0 \)