Chapter 4: Problem 54
$\begin{aligned}
&f(x)=\left|x^{2}-3\right| x|+2| \\
&f(x)= \begin{cases}x^{2}-3 x+2, & 0
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Chapter 4: Problem 54
$\begin{aligned}
&f(x)=\left|x^{2}-3\right| x|+2| \\
&f(x)= \begin{cases}x^{2}-3 x+2, & 0
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\(\sqrt{\mathrm{y}+\mathrm{x}}+\sqrt{\mathrm{y}-\mathrm{x}}=\mathrm{c}\) Squaring both sides. \(2 y+2 \sqrt{y^{2}-x^{2}}=c^{2}\) Differentiating $2 y^{\prime}+\frac{2\left(y y^{\prime}-x\right)}{\sqrt{y^{2}-x^{2}}}=0$ \(y^{\prime}=\frac{x}{y+\sqrt{y^{2}-x^{2}}}=\frac{2 x}{c^{2}}\) Rationilising, we get \(y^{\prime}=\frac{y-\sqrt{y^{2}-x^{2}}}{x}\)
\(f(x)=\frac{x}{1+e^{1 / x}}\) \(f(x)\left(1+e^{1 / x}\right)-x=0\) \(f^{\prime}(x)\left(1+e^{1 / x}\right)-\frac{f(x) e^{l / x}}{x^{2}}-1=0\) \(x^{2} f^{\prime}(x) \frac{(x)}{f(x)}-f(x) e^{1 / x}-x^{2}=0\)
\(f(x)=e^{a x}+e^{b x}\) \(f^{\prime}(x)=a e^{a x}+b e^{b x}\) \(f^{\prime \prime}(x)=a^{2} e^{a x}+b^{2} e^{b x}\) Now \(f^{\prime \prime}(x)-2 f^{\prime}(x)-15 f(x)=0\) $\Rightarrow\left(a^{2}-2 a-15\right) e^{a x}+\left(b^{2}-2 b-15\right) e^{b x}=0$ \(\Rightarrow a^{2}-2 a-15=0 \quad \& \quad b^{2}-2 b-15=0\) a, bare two roots of \(x^{2}-2 x-15=0\) \(\mathrm{ab}=-15\)
\(x=a \cos t+\frac{b}{2} \cos 2 t, \quad y=a \sin t+\frac{b}{2} \sin 2 t\) $\frac{d x}{d t}=-a \sin t-b \sin 2 t, \quad \frac{d y}{d t}=a \cos t+b \cos 2 t$ \(\frac{d y}{d x}=\frac{-(a \cos t+b \cos 2 t)}{a \sin t+b \sin 2 t}\) $\frac{d^{2} y}{d x^{2}}=\left[\begin{array}{l}\frac{(a \sin t+b \sin 2 t)(+a \sin t+2 b \sin 2 t)}{(a \sin t+b \sin 2 t)^{2}} \\ +(a \cos t+b \cos 2 t)(a \cos t+2 b \cos 2 t)\end{array}\right] \times \frac{1}{-(a \sin t+b \sin 2 t)}$ For \(\frac{d^{2} y}{d x^{2}}=0\) \((a \sin t+b \sin 2 t)(a \sin t+2 b \sin 2 t)+(a \cos t+b \cos 2 t)\) \((a \cos t+2 b \cos 2 t)=0\) \(\Rightarrow a^{2}+2 b^{2}+a b \cos t+2 a b \cos t=0\) \(\Rightarrow \cos t=\frac{-\left(a^{2}+2 b^{2}\right)}{3 a b}\)
If \(\mathrm{f}(\mathrm{x})=|\ln | \mathrm{x} \|\), then \(\mathrm{f}^{\prime}(\mathrm{x})\) equals (A) \(\frac{-\operatorname{sgn} \mathrm{x}}{|\mathrm{x}|}\), for \(|\mathrm{x}|<1\), where \(\mathrm{x} \neq 0\) (B) \(\frac{1}{x}\) for \(|x|>1\) and \(-\frac{1}{x}\) for \(|x|<1, x \neq 0\) (C) \(-\frac{1}{x}\) for \(|x|>1\) and \(\frac{1}{x}\) for \(|x|<1\) (D) \(\frac{1}{x}\) for \(|x|>0\) and \(-\frac{1}{x}\) for \(x<0\)
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