allerySolve d²y/dx² - 4 dy/dx + 4y = 0:
Ay = A cos 2x
By = (A + B x) e^(2x) (repeated root)
Cy = A e^x
Dy = A + B x
Answer & Solution
Correct answer: B. y = (A + B x) e^(2x) (repeated root)
**Auxiliary:** m² - 4m + 4 = 0
→ (m-2)² = 0. Repeated root m = 2. Solution: y = (A + Bx) e^(2x).
For repeated roots, second solution has extra x factor.
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