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CBSE Class 12 Math 2022 Term I Solved Paper

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Question : 17 of 50
Marks: +1, -0
The equation of the tangent to the curve y(1+x2)y (1+x^2) =2x=2-x, where it crosses the XX-axis is
We have, equation of the curve y(1+x2)=2x(i)y (1+x^2) =2-x \dots (i)
y(0+2x)+(1+x2)dydx=01   [on differentiating w.r.t.x]   \therefore y \cdot (0+2x) + (1+x^2) \cdot \frac{dy}{dx} = 0-1 \; \text{ [on differentiating w.r.t.x] }\;
2xy+(1+x2)  dydx=1\Rightarrow 2xy + (1+x^2) \; \frac{dy}{dx} = -1
  dydx=  12xy1+x2   (ii)   \Rightarrow \; \frac{dy}{dx} = \; \frac{-1-2xy}{1+x^2} \dots \; \text{ (ii) }\;
Since, the given curve passes through xx- axis i.e., y=0y=0.
O(1+x2)=2x   [using Eq.(i)]   \therefore O (1+x^2) = 2-x \; \text{ [using Eq.(i)] }\;
x=2\Rightarrow x=2
So, the curve passes through the point (2,0)(2,0).
(dydx)(2,0)=12×01+22=15=   slope of the curve   \therefore \left(\frac{dy}{dx}\right)_{(2,0)} = \frac{-1-2 \times 0}{1+2^2} = -\frac{1}{5} = \; \text{ slope of the curve }\;
\therefore slope of tangent to the curve =  15= -\; \frac{1}{5}
\therefore Equation of tangent of the curve passing through (2,0)(2,0) is
y0=  15(x2)y-0 = -\; \frac{1}{5}(x-2)
5y=x+2\Rightarrow 5y = -x + 2
5y+x=2\Rightarrow 5y + x = 2
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