One solution of the different equation y''+y'=0 is y=e^(-x). Use Reduction of Order to find a second linearly independent solution.

blackdivcp

blackdivcp

Answered question

2022-10-23

One solution of the different equation y + y = 0 is y = e x . Use Reduction of Order to find a second linearly independent solution.

Answer & Explanation

Shyla Larson

Shyla Larson

Beginner2022-10-24Added 11 answers

In such problems ie second order linear differential equations when we are given one solution, y 1 we assume the second solution to be of the form, y 2 = v y 1 and substitute y 2 in the given ode and reduce order of the differential equation by using the fact that y 1 is a solution.
Compute: y 2 ,   y 2
y 2 = v y 1 + v y 1 = v e x + v e x = e x ( v + v ) y 2 = e x ( v + v ) + e x ( v + v ) = e x ( v v v + v )
Substitute y 2 ,   y 2 in given differential equation
e x ( v 2 v + v ) + e x ( v + v ) = 0 e x ( v + v ) = 0 v + v = 0
Let u=v’ we get a first order differential equation
u + u = 0 u = u u = e x
Substitute u=v’ in above equation and solve for v
v = e x Integrating we get v = e x
Get second linearly independent solution by substituting v in expression for y 2
y 2 = v e x = c e x e x = c
Hence second linearly independent solution is c

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