Answer:
Step-by-step explanation:
assuming that the complete question is:
If AD = 3 and DB = 9 find AC.
(AC)^2 = AD * AB
y2 = 3 * 12 ( AB = AD + DB ; AB = 3 + 9 =12)
y^2 = 36
y = ± 6
AC = 6 ( AC can not be negative , so reject -6 )
