tolong.... [tex]2 \sqrt{3 \: - \sqrt{5} }[/tex]

(1 - √5)² = (1-√5)(1-√5)
              = 1 -√5 - √5√ + 5
              = 6 - 2√5
              = 2(3 -√5)

2√(3-√5) = 2√ (1/2(1-√5)²)
               = 2 (1-√5)) (√1/2)
               = 2-2√5 (√1/2)