Pre-Cal 12 question
 

I'm not very good at math and I don't like it either. I need it as a preresequite for University(classes i'm taking just use basics from Pre-Cal 12, so i'm not going to be hurt to bad).

Well, here it is. I think i'm trying to make it harder than it is, I do that sometimes...I hate it...

if 1/b-a, 1/2b, 1/b-c are sequences of an arithmetic function, prove that b^2=ac


Any help appreciated....