Chapter 8: Problem 37
$$6 x^{3} y^{\prime \prime \prime}+13 x^{2} y^{\prime \prime}-\left(x^{2}+3 x\right) y^{\prime}-x y=0$$
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Chapter 8: Problem 37
$$6 x^{3} y^{\prime \prime \prime}+13 x^{2} y^{\prime \prime}-\left(x^{2}+3 x\right) y^{\prime}-x y=0$$
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Buckling Columns. In the study of the buckling of a column whose cross section varies, one encounters the equation $$\quad x^{n} y^{\prime \prime}(x)+\alpha^{2} y(x)=0, \quad x>0$$ where x is related to the height above the ground and y is the deflection away from the vertical. The positive constant a depends on the rigidity of the column, its moment of inertia at the top, and the load. The positive integer n depends on the type of column. For example, when the column is a truncated cone [see Figure 8.13(a) on page 474], we have $$n=4$$ (a) Use the substitution \(x=t^{-1}\) to reduce \((45)\) with \(n=4\) to the form \(\frac{d^{2} y}{d t^{2}}+\frac{2}{t} \frac{d y}{d t}+\alpha^{2} y=0, \quad t>0\) (b) Find at least the first six nonzero terms in the series expansion about \(t=0\) for a general solution to the equation obtained in part (a). (c) Use the result of part (b) to give an expansion about \(x=\infty\) for a general solution to \((45) .\)
\(x^{2} y^{\prime \prime}+x y^{\prime}+x^{2} y=0\)
Let \(f(x)=\left\\{\begin{array}{ll}{e^{-1 / x^{2}},} & {x \neq 0} \\ {0,} & {x=0}\end{array}\right.\) Show that \(f^{(n)}(0)=0\) for \(n=0,1,2, \ldots\) and hence that the Maclaurin series for \(f(x)\) is \(0+0+0+\cdots\) which converges for all \(x\) but is equal to \(f(x)\) only when \(x=0 .\) This is an example of a function possessing derivatives of all orders \(\left(\) at \(x_{0}=0\right),\) whose Taylor series converges, but the Taylor series (about \(x_{0}=0 )\) does not converge to the original function! Consequently, this function is not analytic at \(x=0 .\)
$$6 x^{3} y^{\prime \prime \prime}+\left(13 x^{2}-x^{3}\right) y^{\prime \prime}+x y^{\prime}-x y=0$$
$$x(x+1) y^{\prime \prime}+(x+5) y^{\prime}-4 y=0$$
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