Question

The equations of the transverse and conjugate axes of a hyperbola are respectively $x+2y-3=0,2x-y+4=0$ and their respective lengths are $\sqrt{2}$ & $\frac{2}{\sqrt{3}}$. The equation of the hyperbola is

• A. $\frac{2}{5}(2x-y+4{)}^2-\frac{3}{5}(x+2y-3{)}^2=1$
• B. $\frac{2}{5}(x+2y-3{)}^2-\frac{3}{5}(2x-y+4{)}^2=1$
• C. $\frac{5}{2}(2x-y+4{)}^2-\frac{5}{3}(x+2y-3{)}^2=1$
• D. $\frac{5}{2}(x+2y-3{)}^2-\frac{5}{3}(2x-y+4{)}^2=1$

Answer 1

The correct option is A

$\frac{2}{5}(2x-y+4{)}^2-\frac{3}{5}(x+2y-3{)}^2=1$

Given, $2a=\sqrt{2}\Rightarrow a=\frac{1}{\sqrt{2}}$

and $2b=\frac{2}{\sqrt{3}}\Rightarrow b=\frac{1}{\sqrt{3}}$

If we take the two axes as the new coordinate system, and the point of intersection of the axes as the new origin, then in the new coordinate system, the equation of the hyperbola is

$\frac{X^2}{a^2}-\frac{Y^2}{b^2}=1$

$=2X^2-3Y^2=1$

Let $P(x,y)$ be the coordinates of a point on the hyperbola in the original $x-y$ system, then

$X=\frac{|2x-y+4|}{\sqrt{5}}$ and $Y=\frac{|x+2y-3|}{\sqrt{5}}$

[$\because X$ is the distance of a point on the hyperbola from $2x-y+4=0$ and $Y$ is the distance of a point on the hyperbola from $x+2y-3=0$]

So, the required equation is $\frac{2}{5}(2x-y+4{)}^2-\frac{3}{5}(x+2y-3{)}^2=1$