焦点 ((y)^2)/(81)-((x)^2)/(121)=1

解答

焦点

\frac{( y ) ^{2}}{81} - \frac{( x ) ^{2}}{121} = 1

(0, 202), (0, - 202)

求解步骤

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

计算双曲线性质

\frac{y ^{2}}{81} - \frac{x ^{2}}{121} = 1 :

上下开口双曲线，

(h, k) = (0, 0), a = 9, b = 11

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

计算

c :

c = 9^{2} + 1 1^{2} : 202

(0, 0 + 202), (0, 0 - 202)

整理后得

(0, 202), (0, - 202)

f oc i x^{2} - y^{2} = 15

f oc i x^{2} - 10 x = 4 y^{2} - 5

f oc i 2 x^{2} - 2 y^{2} - 20 x + 16 y - 16 = 0

f oc i \frac{y ^{2}}{25} - \frac{x ^{2}}{36} = 1

f oc i \frac{( x - 1 ) ^{2}}{12} - \frac{( y - 2 ) ^{2}}{8} = 1