1.x^2/16+y^2/4=1
a=4,b=2,c=2*3^(1/2)
e=c/a=[3^(1/2)]/2,
焦点：(2*3^(1/2),0),(-2*3^(1/2),0)
顶点坐标：(4,0),(-4,0),(0,2),(0,-2)
2.x^2/9+y^2/81=0
a=9,b=3,c=6*2^(1/2)
e=c/a=[2*2^(1/2)]/3
焦点：(0,6*2^(1/2)),：(0,-6*2^(1/2))
顶点：(3,0),(-3,0),(0,9),(0,-9)