x+3y-6=0与与坐标轴的交点为：(0,2),(6,0)
b=2,c=6时,a^2=b^2+c^2=40
椭圆方程为：x^2/40+y^2/4=1
b=6,c=2时,a^2=b^2+c^2=40
椭圆方程为：x^2/36+y^2/40=1