Diketahui a = 2sqrt 3 + sqrt 5 dan b = 3sqrt 5 - sqrt 3.

Diketahui a = 2sqrt 3 + sqrt 5 dan b = 3sqrt 5 - sqrt 3. Nilai ab = a. 5sqrt 15+9 b. 5sqrt 15+21 c. 5sqrt 15-9 d. 5sqrt 15-21