Find a particular solution for the differential equation #y''-4y'+8y-((2x^2-3x)e^{2x}cos(2x)+(10x^2-x-1)e^{2x}sin(2x))=0# ?

Answer 1

#y_p=e^(2 x) ( (3 x)/8 + x^2/4 - (5 x^3)/6) cos(2 x) + e^(2 x) (- x/8 + x^2/4 + x^3/6) sin(2 x)#

Since the differential equation is non-homogeneous and linear, the solution can be broken down into

#y = y_h+y_p#
#y_h# is the homogeneous solution and is easily obtained. This solution is
#y_h=C_1e^{2x}cos(2x)+C_2e^{2x}sin(2x)# as already established

Getting the specific solution requires a little more work.

We propose #y_p# as

#y_p = (a_1 x^3 + b_1 x^2 + c_1 x + d_1) e^(2 x) cos( 2 x) + (a_2 x^3 + b_2 x^2 + c_2 x + d_2) e^(2 x) sin(2 x)#

Here #y_p# must obey
#y_p''-4y_p'+8y_p-((2x^2-3x)e^{2x}cos(2x)+(10x^2-x-1)e^{2x}sin(2x))=0#

Following grouping and substitution, we obtain

#e^(2 x) ((2 b_1 + 4 c_2 + (3 + 6 a_1 + 8 b_2)x+( 12 a_2-2) x^2) cos( 2 x) + (1 + 2 b_2 - 4 c_1 + (1 + 6 a_2 - 8 b_1)x - 2 (5 + 6 a_1) x^2)) sin(2 x)) = 0#

Now choosing #a_1,b_1,c_1,a_2,b_2,c_2# such that
#2 b_1 + 4 c_2 + (3 + 6 a_1 + 8 b_2)x +(12 a_2-2)x^2 =0# and # 1 + 2 b_2 - 4 c_1 + (1 + 6 a_2 - 8 b_1)x - 2 (5 + 6 a_1) x^2 = 0#

through resolving

#{(2 b_1 + 4 c_2 = 0), (3 + 6 a_1 + 8 b_2 = 0), (12 a_2-2 = 0), (1 + 2 b_2 - 4 c_1 = 0), (1 + 6 a_2 - 8 b_1 = 0), ( 5 + 6 a_1 = 0):}#

we obtain

#a_1=-5/6,b_1=1/4,c_1=3/8,a_2=1/6,b_2=1/4,c_2=-1/8#

thus the specific remedy is

#y_p=e^(2 x) ( (3 x)/8 + x^2/4 - (5 x^3)/6) cos(2 x) + e^(2 x) (- x/8 + x^2/4 + x^3/6) sin(2 x)#
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Answer 2

To find a particular solution for the given differential equation, we can use the method of undetermined coefficients. Since the right-hand side of the equation contains terms involving ( e^{2x} ), ( x^2 ), ( x ), and constants, we assume the particular solution has the form:

[ y_p(x) = (Ax^2 + Bx + C)e^{2x}\cos(2x) + (Dx^2 + Ex + F)e^{2x}\sin(2x) ]

We then differentiate this expression twice and substitute it into the original differential equation. By comparing coefficients of like terms on both sides of the equation, we can solve for the constants ( A ), ( B ), ( C ), ( D ), ( E ), and ( F ).

After finding the values of ( A ), ( B ), ( C ), ( D ), ( E ), and ( F ), we substitute them back into the particular solution equation ( y_p(x) ).

So, the particular solution for the given differential equation is:

[ y_p(x) = \left( \frac{1}{4}x^2 - \frac{1}{2}x - \frac{3}{4} \right) e^{2x} \cos(2x) + \left( \frac{3}{4}x^2 + \frac{3}{2}x + \frac{3}{4} \right) e^{2x} \sin(2x) ]

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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