Chapter 12: Problem 1
By Leibniz' rule, write the formula for \(\left(d^{n} / d x^{n}\right)(u v)\).
Short Answer
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chapter 12: Problem 1
By Leibniz' rule, write the formula for \(\left(d^{n} / d x^{n}\right)(u v)\).
These are the key concepts you need to understand to accurately answer the question.
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Show that any polynomial of degree \(n\) can be written as a linear combination of Legendre polynomials with \(l \leq n\)
Solve the following differential equations by series and also by an elementary method and verify that your solutions agree. Note that the goal of these problems is not to get the answer (that's easy by computer or by hand) but to become familiar with the method of series solutions which we will be using later. Check your results by computer. $$x y^{\prime}=y$$
Solve the following differential equations by the method of Frobenius (generalized power series). Remember that the point of doing these problems is to learn about the method (which we will use later), not just to find a solution. You may recognize some series [as we did in (11.6)] or you can check your series by expanding a computer answer. $$x y^{\prime \prime}-y^{\prime}+9 x^{5} y=0$$
Solve the following differential equations by the method of Frobenius (generalized power series). Remember that the point of doing these problems is to learn about the method (which we will use later), not just to find a solution. You may recognize some series [as we did in (11.6)] or you can check your series by expanding a computer answer. $$x^{2} y^{\prime \prime}+2 x^{2} y^{\prime}-2 y=0$$
Show that $$\frac{d^{l-m}}{d x^{l-m}}\left(x^{2}-1\right)^{l}=\frac{(l-m) !}{(l+m) !}\left(x^{2}-1\right)^{m} \frac{d^{l+m}}{d x^{l+m}}\left(x^{2}-1\right)^{l}$$ Hint: Write \(\left(x^{2}-1\right)^{l}=(x-1)^{l}(x+1)^{l}\) and find the derivatives by Leibniz' rule.
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