34) √(a²+6ab+9b²), a=5, b=-4

1. Recognize the expression under the radical as a perfect square: √((a+3b)²).
2. Simplify: |a+3b|.
3. Substitute a=5 and b=-4: |5 + 3(-4)| = |5 - 12| = |-7| = 7.