Practicing Success
The point of intersection of the tangents drawn to the curve $x^2 y=1-y$ at the points where it is met by the curve $x y=1-y$, is given by |
(0, -1) (1, 1) (0, 1) none of these |
(0, 1) |
Solving the two equations, we get $x^2y=xy \Rightarrow xy(x-1) = 0 \Rightarrow x = 0, y = 0, x= 1$ Since y = 0 does not satisfy the two equations. So, we neglect it. Putting x = 0 in the either equation, we get x = 1 Now, putting x = 1 in one of the two equations we obtain y = 1/2. Thus, the two curves intersect at (0, 1) and (1, 1/2). Now, $x^2 y=1-y \Rightarrow x^2 \frac{d y}{d x}+2 x y =-\frac{d y}{d x} \Rightarrow \frac{d y}{d x}=-\frac{2 x y}{x^2+1}$ $\Rightarrow \left(\frac{d y}{d x}\right)_{(0,1)}=0$ and $\left(\frac{d y}{d x}\right)_{(1,1 / 2)}=-\frac{1}{2} $ The equations of the required tangents are $y-1=0(x-0)$ and $y-\frac{1}{2}=\frac{-1}{2}(x-1)$ $\Rightarrow y=1$ and $x+2 y-2=0$ These two tangents intersect at (0, 1). |