# Differential Equations

Free Version
Moderate

DIFFEQ-XHJGGN

Consider a laterally loaded long pile in soil. According to the Euler-Bernoulli beam theory, the equation about the displacement may be written as $y''''+xy=0$ where $x\in[0,\infty)$.

One can change this equation into a first order equation by taking the Laplace Transform. Define $Y(s)=\int_0^{\infty}e^{-xs}y(x)dx$.

The equation that $Y(s)$ satisfies is

A

$s^4Y-Y'=0$

B

$Y'-s^4Y=As^3+Bs^2+Cs+D$ for some constants $A,B,C,D$

C

$s^4Y+Y'=0$

D

$s^4Y+Y'=As^3+Bs^2+Cs+D$ for some constants $A,B,C,D$