Question

Tolong dong no12,13dan,14

Answer 1

12.
L=a x t x 1/2
10 x 2 = (3+√5) x t 
20 = (3+√5) x t
t = 20/3+√5 x (3-√5/3-√5)
t=60-20√5/9-5
t=60-20√5/4
t=15-5√5 cm