Solving D.E. with Variation of Parameters Technique

AI Thread Summary
To solve the differential equation x^2y'' - xy' + y = x^3 using the variation of parameters technique, the first step is to transform the equation into a standard form by ensuring the coefficient of y'' is 1. This leads to the homogeneous equation y'' - (1/x)y' + (1/x^2)y = 0, which simplifies to a characteristic equation m^2 - 2m + 1 = 0, yielding the solution C_1x + C_2tx. The discussion highlights confusion around the next steps, particularly with the term C_2tx, and suggests that transforming the equation into a linear one with constant coefficients may be necessary. The participants also clarify that the equation is an Euler equation, and a substitution involving x = e^t is recommended to proceed.
RadiationX
Messages
255
Reaction score
0
I need to solve this D.E.

x^2y''-xy' + y = x^3

i'm supposed to use the variation of parameters technique.

in that technique i need to get a coeffecient of 1 in the first postion of y'' and then sove the homogenous D.E.

y''-\frac{y'}{x} +\frac{y}{x^2}=0

the above leads to

m^2-2m +1=0

now solving this i get

C_1x +C_2tx

my problem is that i don't know how to move forward with
C_2tx

how do i proceed
 
Last edited:
Physics news on Phys.org
It's an Euler equation.You need to transform it into a linear equation with constant coeffs.Read the theory again and identify the substitution you need.

Daniel.
 
do you mean that this is a Bernoulli equation?
 
I told u it was/is an Euler eqn.

Make the sub

x=e^{t}

y(x)\longrightarrow \bar{y}(t)

Daniel.
 
Last edited:
ok. i'll figure it out
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'Collision of a bullet on a rod-string system: query'
In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top