Undetermined Coefficient with repeated roots

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SUMMARY

The discussion focuses on solving the differential equation y" + 2y' - 3y = x^2*e^x using the method of undetermined coefficients, specifically addressing the challenge of repeated roots. The roots identified are y1 = -3 and y2 = 1, leading to the complementary solution involving e^x. The proposed particular solution yp is suggested to be in the form of either x * (x^2*A*e^x) or x * (Ax^2 + Bx + C)e^x to account for the repeated root e^x. Additionally, the setup for a problem involving yp = P(x)*e^(ax)*cos(bx) is discussed, emphasizing the combination of particular integrals for different polynomial degrees.

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Homework Statement



The problem is: y" + 2y' - 3y = x^2*e^x

Homework Equations





The Attempt at a Solution



I know the roots are y1 = -3 and y2 = 1, becoming e^x.

I'm not sure how to set my yp up though with the repeating e^x.

My ideas are yp = x * (x^2*A*e^x) or x * (Ax^2 + Bx + C)e^x.

I was also curious on the setup of a problem where yp = P(x)*e^ax* cos(bx).
 
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since '1' is a root, the PI for ex is xex, and PI for x2 is Ax2+Bx+C, so put those 2 together

yp=xex(Ax2+Bx+C)
 

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