设椭圆(X²/m)+(y²/n)=1的焦点在y轴上m∈{1,2,3,4,5},n∈{1,2,3,4,5,6,7}则这样的椭圆个数_____
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![设椭圆(X²/m)+(y²/n)=1的焦点在y轴上m∈{1,2,3,4,5},n∈{1,2,3,4,5,6,7}则这样的椭圆个数_____](/uploads/image/z/4316166-54-6.jpg?t=%E8%AE%BE%E6%A4%AD%E5%9C%86%EF%BC%88X%26%23178%3B%2Fm%EF%BC%89%2B%EF%BC%88y%26%23178%3B%2Fn%EF%BC%89%3D1%E7%9A%84%E7%84%A6%E7%82%B9%E5%9C%A8y%E8%BD%B4%E4%B8%8Am%E2%88%88%EF%BD%9B1%2C2%2C3%2C4%2C5%EF%BD%9D%2Cn%E2%88%88%EF%BD%9B1%2C2%2C3%2C4%2C5%2C6%2C7%EF%BD%9D%E5%88%99%E8%BF%99%E6%A0%B7%E7%9A%84%E6%A4%AD%E5%9C%86%E4%B8%AA%E6%95%B0_____)
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设椭圆(X²/m)+(y²/n)=1的焦点在y轴上m∈{1,2,3,4,5},n∈{1,2,3,4,5,6,7}则这样的椭圆个数_____
设椭圆(X²/m)+(y²/n)=1的焦点在y轴上m∈{1,2,3,4,5},n∈{1,2,3,4,5,6,7}
则这样的椭圆个数_____
设椭圆(X²/m)+(y²/n)=1的焦点在y轴上m∈{1,2,3,4,5},n∈{1,2,3,4,5,6,7}则这样的椭圆个数_____
焦点在y轴上m∈{1,2,3,4,5},n∈{1,2,3,4,5,6,7}
那么有n>m
n=2,m=1
n=3,m=1,2
n=4,m=1,2,3
n=5,m=1,2,3,4
n=6,m=1,2,3,4,5
n=7,m=1,2,3,4,5
共有:1+2+3+4+5+5=20个椭圆
if m=n
(x²/m)+(y²/n)=1 是圆形
椭圆个数 = 5x7 - 5
= 35 -5
= 30