4x²-9=0
(2x)²=3²
2x=±3
x=±3/2
2x²+3x-1=0
x=[-3±√(3²+2×4)]/(2×2)=(-3±√17)/4
(x-1)²-2(x²-1)=0
x²-2x+1-2x²+2=0
x²+2x-3=0
(x-1)(x+3)=0
x=1,x=-3