Chapter 5: Problem 6
\(f^{\prime}(x)= \begin{cases}-2 x, & x<0 \\ 2 x, & x \geq 0\end{cases}\) eqn of tangent $\rightarrow \quad y-y_{1}=2 x_{1}\left(x-x_{1}\right), x \geq 0$ \(y-y_{2}=-2 x_{2}\left(x-x_{2}\right) x<0\)
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Chapter 5: Problem 6
\(f^{\prime}(x)= \begin{cases}-2 x, & x<0 \\ 2 x, & x \geq 0\end{cases}\) eqn of tangent $\rightarrow \quad y-y_{1}=2 x_{1}\left(x-x_{1}\right), x \geq 0$ \(y-y_{2}=-2 x_{2}\left(x-x_{2}\right) x<0\)
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For \(y=x(c-x)\) \(\frac{d y}{d x}=c-2 x\) For \(y=x^{2}+a x+b\) \(\frac{d y}{d x}=2 x+a\) At \((1,0)\) \(0=(C-1) \Rightarrow C=1\) \(0=1+a+b, 1-2=2+a\) \(\Rightarrow \quad a=-3\) \(\Rightarrow b=2\)
\(y=\frac{a x}{1+x}=a-\frac{a}{1+x}\) \(\frac{d y}{d x}=\frac{a}{(1+x)^{2}}=-1\) \(a=-\left(1+x_{1}\right)^{2}\) eqn of tangent \(y-\frac{a x_{1}}{1+x_{1}}=-1\left(x-x_{1}\right)\) \(\mathrm{y}+\mathrm{x}=\mathrm{x}_{1}+\frac{\mathrm{ax}_{1}}{1+\mathrm{x}_{1}}\) \& \(y-3=-x \Rightarrow y+x=3\) \(\Rightarrow \mathrm{x}_{1}+\frac{\mathrm{ax}_{1}}{1+\mathrm{x}_{1}}=3\) \(\Rightarrow \mathrm{x}_{1}-\mathrm{x}_{1}\left(1+\mathrm{x}_{1}\right)=3\)
\(f_{1}^{\prime}(x)=2 x-1 \quad \& \quad f_{2}^{\prime}(x)=3 x^{2}-2 x-2\) \(\Rightarrow 2 x_{1}-1=3 x_{2}^{2}-2 x_{2}-2\) \(\Rightarrow 3 x_{2}^{2}-2 x_{2}-2 x_{1}-1=0\) For \(\mathrm{x}_{2}\) be real, \(\mathrm{D} \geq 0\) \(4-4\left(2 x_{1}+1\right)(3)\) \(4-24 x_{1}-12\) \(\Rightarrow-\left(24 x_{1}+8\right)\) There can be infinite such values of \(\mathrm{x}_{\mathrm{l}}\)
\(f(0)<0\) \(\Rightarrow \mathrm{a}^{2}+\mathrm{a}-2<0\) \(\Rightarrow a \in(-2,1)\) Integral values of a are \(-1,0\).
Let \(y=m x+\frac{1}{m}\) be tangent to \(y^{2}=4 x\) eqn of normal at \(\left(x_{1}, y_{1}\right)\) to \(x^{2}=4\) by is \(y-y_{1}=-\frac{2 b}{x_{1}}\left(x-x_{1}\right)\) \(\Rightarrow y=-\frac{2 b}{x_{1}} x+\frac{x_{1}^{2}}{4 b}+2 b\) Comparing two eqn \(\mathrm{m}=-\frac{2 \mathrm{~b}}{\mathrm{x}_{1}}\) \(\frac{\mathrm{x}_{1}^{2}}{4 \mathrm{~b}}+2 \mathrm{~b}=\frac{1}{\mathrm{~m}}\) Using (I) \& (II)
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