4x²+4x-9y²+1=0
(2x+1)²-9y²=0
y²=(2x+1)²/9
(2x+1)²/9-2x-1=0
4x²-14x-8=0
2x²-7x-4=0
(2x+1)(x-4)=0
2x+1=0 x=-1/2 y=0
x-4=0 x=4 y=±3
所以x=-1/2 y=0 或x=4 y=3或x=4 y=-3