If the tangent to the curve xy + ax + by = 0 at (1, 1) is inclined at an angle $\tan ^{-1} 2$ with x-axis, then
Answer & explanation
Correct answer: option 2
The point (1, 1) lies on the curve xy + ax + by = 0
∴ $a+b=-1$ ........(i)
Now, $x y+a x+b y=0$
$\Rightarrow x \frac{d y}{d x}+y+a+b \frac{d y}{d x}=0$
$\Rightarrow \left(\frac{d y}{d x}\right)_{(1,1)}=-\frac{a+1}{b+1}$ .....(ii)
Since the tangent makes an angle $\tan ^{-1} 2$ with x-axis.
∴ Slope of the tangent = 2
$\Rightarrow 2=-\frac{a+1}{b+1} \Rightarrow a+2 b=-3$ .......(iii)
Solving (i) and (iii), we get a = 1, b = -2