Solutions of the differential equation x^2y’’-4xy’+6y=0. In one of my test it given to pro

Libby Boone

Libby Boone

Answered question

2022-04-21

Solutions of the differential equation x2y4xy+6y=0.
In one of my test it given to prove that x3 and x2|x| are linear independent solutions of the differential equation x2y4xy+6y=0 on R( here x is independent variable).
But according to me it’s Cauchy Euler equation having general solution as y=c1x3+c2x2, where c1 and c2 are arbitrary constants. How can be x2|x| a solution of given ODE as I am unable to find its by giving particular values of constants c1 and c2? Please help me to solve it.

Answer & Explanation

Isla Preston

Isla Preston

Beginner2022-04-22Added 12 answers

Explanation:
The differential equation has a singularity at x=0, so the Existence and Uniqueness Theorem doesn't apply there. On each of the intervals (,0) and (0,) where the theorem does apply, you have two-parameter families of solutions. But it turns out any solution on (,0) and any solution on (0,) with the same c2 can be put together to make a solution on R.
Leia Wiggins

Leia Wiggins

Beginner2022-04-23Added 18 answers

Step 1
c1x3+c2x2
is not the general solution of the Cauchy-Euler equation.
Step 2
If you set x=eu, you indeed linearize the original equation to
y¨5y˙+6y=0
with the obvious solution
y=c3e3u+c2e2u=c3x3+c2x2.
But recall that by our change of variable, x was assumed positive. Now we can solve again by setting x=eu and get a solution of a similar shape, but the constants have no reason to be equal on both sides.

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