5) Solve the equation t²y" + 4ty' +2y=0, knowing that this is an Euler equation.
Accepted Solution
A:
To solve the given differential equation t²y" + 4ty' + 2y = 0, we can assume a solution of the form y(t) = t^m, where m is a constant. This will allow us to convert the equation into an algebraic equation in terms of m. This is a standard technique for solving Euler equations.
First, let's find the first and second derivatives of y(t):
y(t) = t^m
y'(t) = mt^(m-1)
y''(t) = m(m-1)t^(m-2)
Now, substitute these derivatives into the original equation:
t²y'' + 4ty' + 2y = 0
t²[m(m-1)t^(m-2)] + 4t[mt^(m-1)] + 2t^m = 0
Now, simplify and factor out t^(m-2) (the lowest power of t):
m(m-1)t^m + 4mt^m + 2t^m = 0
Next, combine the terms with t^m:
t^m [m(m-1) + 4m + 2] = 0
Now, we have an equation involving m:
m(m-1) + 4m + 2 = 0
Let's simplify this equation:
m^2 - m + 4m + 2 = 0
m^2 + 3m + 2 = 0
Now, we can solve this quadratic equation for m. We can factor it:
(m + 2)(m + 1) = 0
So, we have two possible values for m:
1. m + 2 = 0
m = -2
2. m + 1 = 0
m = -1
Now that we have found the values of m, we can write down the two linearly independent solutions for y(t) based on these values:
1. For m = -2:
y₁(t) = t^(-2)
2. For m = -1:
y₂(t) = t^(-1)
So, the general solution to the Euler equation t²y" + 4ty' + 2y = 0 is the linear combination of these two solutions:
y(t) = C₁t^(-2) + C₂t^(-1)
Where C₁ and C₂ are arbitrary constants that can be determined based on initial conditions or boundary conditions if they are given.