Question 115081
Solve the following non-linear system by substitution. 
x^2+y^2=16
x-2y=0
-----------
x = 2y
Substitute into the 1st equation to solve for "y":
(2y)^2 + y^2 = 16
4y^2 + y^2 = 16
5y^2 = 16
y^2 = 16/5
------------
y = 4/sqrt(5) = (4/5)sqrt(5) 
OR 
y = (-4/5)sqrt5
-----------------
Substitute into x = 2y to get:
x = 2[(4/5)sqrt5] = (8/5)sqrt(5)
OR
x = 2(-4/5)sqrt5 = (-8/5)sqrt(5)
=====================
Cheers,
Stan H.