Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 1 - First-Order Differential Equations - 1.2 Basic Ideas and Terminology - Problems: 26

Answer

$y(x) = \frac{1}{2}x(5x^{3} - 3)$ satisfies the differential equation $(1-x^{2})y" - 2xy' + 12y = 0$

Work Step by Step

The Legendre differential equation of 3rd order is: $(1-x^{2})y" - 2xy' + 3(4y) = (1-x^{2})y" - 2xy' + 12y = 0$ Given that $y(x) = \frac{1}{2}x(5x^{3} - 3) = \frac{5x^{3}}{2} - \frac{3x}{2}$ is the solution of the equation above, differentiating it should get: $y'(x) = \frac{3}{2}(5x^{2} - 1)$ $y"(x) = 15x$ Substitute $y(x)$, $y'(x)$ and $y"(x)$ into the above differential equation: $15x(1 - x^{2}) - 2x(\frac{3}{2}(5x^{2} - 1)) + 12(\frac{5x^{3}}{2} - \frac{3x}{2})$ = $x^{3}( -15 - 15 + 30) + x(15 + 3 - 18) =0$ As such, $y(x) = \frac{1}{2}x(5x^{3} - 3)$ satisfies the differential equation $(1-x^{2})y" - 2xy' + 12y = 0$.
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