抛物线x^2=4y上的一点M到焦点的距离为8,点M到准线的距离为多少?点M的纵坐标是多少
人气:471 ℃ 时间:2020-04-05 15:47:00
解答
焦点坐标(0,1),准线方程是y=-1
设M坐标是(a,a^2/4)
M到焦点的距离是8,有关系式a^2+(a^2/4-1)^2=64
化简方程有:(a^2-36)(a^2+28)=0
解出a=6或-6
M点的纵坐标是:9
到准线的距离是9-(-1)=10
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