x²+6xy+9y²=16
x-3y=-2
(x+3y)²=16
x=-2+3y
(-2+3y+3y)²=16
(-2+6y)²=16
-2+6y=-4 ∨ -2+6y=4
6y=-2 ∨ 6y=6
y=-1/3 ∨ y=1
x=-2+3*(-1/3)
x=-2-1
x=-3
x=-2+3*1
x=-2+3
x=1
(-3,-1/3),(1,1)
