31. 在椭圆x216+y29=1(a>b>0)\frac{{x}^{2}}{16}+\frac{{y}^{2}}{9}=1(a>b>0)16x2+9y2=1(a>b>0)中,以点M(2,32)M(2,\frac{3}{2})M(2,23)为中点的弦所在的直线方程为((( )))