Solve d²y/dx² - 4 dy/dx + 4y = 0:
- y = A cos 2x
- y = (A + B x) e^(2x) (repeated root)
- y = A e^x
- y = A + B x
Show answer and 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.