Evil mathematic monsters

[Mateusz_Zboj]

Episode: Alliance of Draculus Sequenciulus and El Quad Equatius.

27,x,y is geometric progression
x,y,(-3) is arithmetic progression

The x is same for both progressions.
Find x,y.

There will be some quadratic equations for sure since I got something like x^2-13.5x+40.5 and the delta was positive.

I am not sure how to do this.

EDIT:
Fixed.

[MagicManICT]

Already have the answers for you. I'll PM so not to spoil it for anyone else.

edit: On second thought, no, I'm not going to PM them. It looks like you have the right idea, though you're probably going about it the wrong way. it looks like this is a problem for school, so I'm not going to help anyone cheat. It's really very simple and you'll kick yourself for not getting it sooner when you figure it out.

second edit: if anyone else wants the answer, I'll be happy to PM them and explain it.

final edit (I promise): same thing works for any x, y in a sequence if you pick appropriate first value of the geometric sequence and third value of the arithmetic sequence.

[Mateusz_Zboj]

Lol what kind of cheat? Is learning called a cheating now too?
I already figured out btw.