I took two 5mg vicodins about two weeks ago will I test positive.
In the past nine months I probably did this 3 times and had a prescription for ten Percocet about 4 months ago. Will the legit prescription save me?

In all likelihood the use described will not be detected. Hair testing is very effective at identifying chronic drug use but not occasional users.*

If usage was detected however Vicodin (Hydrocodone) and Percocet (Oxycodone) break down into different metabolites and can easily be distinguished at the confirmatory level of testing.

*Galanter & Kleber, 2011 Psychotherapy for the Treatment of Substance Abuse, American Psychiatric Publishing, Wash, DC, p. 58

William J. Closson, PhD, Forensic Toxicology Services: A positive hair test result indicates “The individual was most likely a chronic user of the drug detected during the time indicated by the length of the hair.”

Jim Turnage (2011), Forensic DNA & Drug Testing Services, Inc in presentation to Dallas TX Bar Association. p. 15 "It takes multiple uses to test positive in hair under normal drug use. A one -time use will not be above the cutoff level." p. 15