Chapter 5: Problem 73
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 \((1,0)\) \(0=(C-1) \Rightarrow C=1\) \(0=1+a+b, 1-2=2+a\) \(\Rightarrow \quad a=-3\) \(\Rightarrow b=2\)
Chapter 5: Problem 73
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 \((1,0)\) \(0=(C-1) \Rightarrow C=1\) \(0=1+a+b, 1-2=2+a\) \(\Rightarrow \quad a=-3\) \(\Rightarrow b=2\)
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Get started for free\(y^{3}=27 x\) \(3 y^{2} \frac{d y}{d x}=27 \frac{d x}{d t}\) \(\frac{3 y^{2}}{27}<1\) \(y^{2}<9 \Rightarrow y \in(-3,3)\)
\(y=\left(x_{1}-x_{2}\right)^{2}+\left(x_{1}-4-\frac{x_{2}^{2}}{4}\right)^{2}\) Min value of \(y\) is shortest distance between \(y=x-4\) \& \(y=\frac{x^{2}}{4}\) slope of normal \(=-1\) \(\frac{d y}{d x}=\frac{x}{2}\) \(-\frac{d x}{d y}=\frac{-2}{x}=-1\) \(\mathrm{x}=2\)
\(y=\frac{a x}{1+x}=a-\frac{a}{1+x}\) \(\frac{d y}{d x}=\frac{a}{(1+x)^{2}}=-1\) \(a=-\left(1+x_{1}\right)^{2}\) eqn of tangent \(y-\frac{a x_{1}}{1+x_{1}}=-1\left(x-x_{1}\right)\) \(\mathrm{y}+\mathrm{x}=\mathrm{x}_{1}+\frac{\mathrm{ax}_{1}}{1+\mathrm{x}_{1}}\) \& \(y-3=-x \Rightarrow y+x=3\) \(\Rightarrow \mathrm{x}_{1}+\frac{\mathrm{ax}_{1}}{1+\mathrm{x}_{1}}=3\) \(\Rightarrow \mathrm{x}_{1}-\mathrm{x}_{1}\left(1+\mathrm{x}_{1}\right)=3\)
eqn of normal $\sin t / 2 y-a\left[2 \sin \frac{t}{2} \sin t-\sin 2 t \sin \frac{t}{2}\right]$ $$ =x \cos \frac{t}{2}-a\left[2 \cos t \cos \frac{t}{2}+\cos 2 t \operatorname{tos} \frac{t}{2}\right] $$ $\Rightarrow x \cos \frac{t}{2}-y \sin \frac{t}{2}=a\left[\begin{array}{c}2 \cos t \cos \frac{t}{2}-2 \sin t \sin \frac{t}{2} \\ +\cos 2 \operatorname{t} \cos \frac{t}{2}+\sin 2 t \sin \frac{t}{2}\end{array}\right]$ \(=a\left[2 \cos \frac{3 t}{2}+\cos \frac{3 t}{2}\right]\) \(=3 a \cos \frac{3 t}{2}\)
\(y=\frac{x^{2}}{4}-3 x+10\) For \(y=2-\frac{x^{2}}{4}\) eqn of tangent \(y-2=m x+m^{2}\) Solving (II) \& (I) \(m x+2+m^{2}=\frac{x^{2}}{4}-3 x+10\) \(\Rightarrow \frac{x^{2}}{4}-(m+3) x+\left(8-m^{2}\right)=0\) \(\mathrm{D}=0\) \((m+3)^{2}-\left(8-m^{2}\right)=0\) \(2 m^{2}+6 m+1=0\) \(\mathrm{m}_{1}+\mathrm{m}_{2}=-3\)
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