焦点 9y^2-16x^2=81

解答

焦点

9 y^{2} - 16 x^{2} = 81

(0, \frac{15}{4}), (0, - \frac{15}{4})

求解步骤

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

计算双曲线性质

9 y^{2} - 16 x^{2} = 81 :

上下开口双曲线，

(h, k) = (0, 0), a = 3, b = \frac{9}{4}

(0, 0 + c), (0, 0 - c)

计算

c :

c = 3^{2} + (\frac{9}{4})^{2} : \frac{15}{4}

(0, 0 + \frac{15}{4}), (0, 0 - \frac{15}{4})

整理后得

(0, \frac{15}{4}), (0, - \frac{15}{4})