焦点 ((y-2)^2}{40}-\frac{(x-4)^2)/9 =1

解答

焦点

\frac{( y - 2 ) ^{2}}{40} - \frac{( x - 4 ) ^{2}}{9} = 1

(4, 9), (4, - 5)

求解步骤

(h, k + c), (h, k - c)

计算双曲线性质

\frac{( y - 2 ) ^{2}}{40} - \frac{( x - 4 ) ^{2}}{9} = 1 :

上下开口双曲线，

(h, k) = (4, 2), a = 210, b = 3

(4, 2 + c), (4, 2 - c)

计算

c :

c = (210)^{2} + 3^{2} : 7

(4, 2 + 7), (4, 2 - 7)

整理后得

(4, 9), (4, - 5)