1)

 Which of the following is INCORRECT for the hyperbola   $x^{2}-2y^{2}-2x+8y-1=0$

 


A) Its eccentricity is $\sqrt{2}$

B) Length of the transverse axis is 2$\sqrt{3}$

C) Length of the conjugate axis is 2$\sqrt{6}$

D) Latus rectum is 4$\sqrt{3}$

Answer:

Option A

Explanation:

The equation of the hyperbola  is 

 $x^{2}-2y^{2}-2x+8y-1=0$

 or   $ (x-1)^{2}-2(y-2)^{2}+6=0$

 or   $\frac{(x-1)^{2}}{-6}+\frac{(y-2)^{2}}{3}=1$

or  $\frac{(y-2)^{2}}{3}-\frac{(x-1)^{2}}{6}=1$     .....(i)

 or  $\frac{Y^{2}}{3}-\frac{X^{2}}{6}=1$    

 where X =x-1  and Y= y-2 ....(ii)

$\therefore$  The centre =(0,0,) in X-Y co-ordinates 

$\therefore$  The centre = (1,2) in the x-y co-ordinates using (ii)

 If the transverse axis be length 2a, than a  = $\sqrt{3}$, since in the equation (i) the tansverse axis is parallel to the y-axis

 If the conjugate axis is of length 2b n, then b= $\sqrt{6}$

But   $b^{2}=a^{2}(e^{2}-1)$

$\therefore$   $6=3(e^{2}-1), \therefore e^{2}=3$   or  $ e=\sqrt{3}$

The  length of the transverse axis =2$\sqrt{3}$

 The length of the conjugate axis =2$\sqrt{6}$

 Latus rectum =   $\frac{2b^{2}}{a}=\frac{2\times6}{\sqrt{3}}=4\sqrt{3}$