Solving the differential equation x^2y′′+xy′−y=x^2

Trace Glass

Trace Glass

Answered question

2022-10-27

x 2 y + x y y = x 2
My attempt:
Divided by x 2 :
y + y x y x 2 = 1
Now to solve the homogenous equation using Euler's method
y + y x y x 2 = 0
To look for solution y = x r
so y = r x r 1
y = r ( r 1 ) x r 2
So:
r ( r 1 ) x r 2 + r x r 1 x x r x 2 = 0
Divided by x r :
r ( r 1 ) x 2 + r x 1 x 1 x 2 = 0
Is it correct so far?
My problem: I don't know how to find r 1 , r 2

Answer & Explanation

snowman8842

snowman8842

Beginner2022-10-28Added 12 answers

We have
r ( r 1 ) x 2 + r x 1 x 1 x 2 = 0
Multiplying through by x 2 yields
r ( r 1 ) + r 1 = 0 r = ± 1
So that you get your complementary solution as y = x and y = 1 x .
Taniya Melton

Taniya Melton

Beginner2022-10-29Added 5 answers

y c = A x + B x
Now since the D.E. is linear, also account for a particular solution, i.e.
y p = s x 2 so y + y x y x 2 = 2 s + 2 s s = 3 s = 1 giving s = 1 3 , so y p = 1 3 x 2
Then the full solution is
y = A x + B x + 1 3 x 2

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