Question

The equation of a tangent to the hyperbola $4x^2-5y^2=20$ parallel to the line $x-y=2$ is :

• A. $x-y+9=0$
• B. $x-y+7=0$
• C. $x-y+1=0$
• D. $x-y-3=0$

Answer 1

Answer: (C)

Hyperbola $\frac{x^2}{5}-\frac{y^2}{4}=1$
slope of tangent = $1$
equation of tangent $y=x\pm \sqrt{5-4}$
$\Rightarrow y=x\pm 1$
$\to y=x+1$ or $y=x-1$