Quote by frozen7
( l 2x l ^2 )  2 l 2x l = 15
((2x)^2) = 15 + 2 l 2x l 1
((2x)^2) = 15  2 l 2x l2
Am I doing correctly?

How did you get 2?
I
think that you intended to drop the absolute value signs.
Yes, 2x
^{2}l= (2x)
^{2}. Either 2x= (2 x) (if 2x>= 0) or 2x= (2x)
Change the absolute values to parentheses and you will correct.