Using Second Order Differentiation how do you solve y4y5ex4x
Using Second Order Differentiation, how do you solve y\'\'+4y=5e^x-4x?
Solution
Characteristic equation is:
r^2+4 = 0
the roots are:
r = -2i , 2i
So the homogeneous part of the solution is:
yh = Asin(2x) + Bcos(2x)
To find particular solution we have:
p(x) = 5e^x - 4x -> yp = Ce^x + Dx + E
Thus:
yp\' = Ce^x + D
yp\" = Ce^x
and
yp\" + 4yp = 5Ce^x + 4Dx + 4E = 5e^x - 4x
5C = 5 -> C = 1
4D = -4 -> D = -1
4E = 0 -> E = 0
So the final solution is:
y = yh+ yp = Asin(2x) + Bcos(2x) + e^x - x
