a) 3x^2 + 2x - 1 = 0 =>3x^2 + 3x - x -1 =0 => (3x^2 + 3x) - (x +1)=0 => 3x(x+1) - (x+1) =0 => (x+1)(3x-1)=0 => x+1=0 hoặc 3x-1=0
TH1: x+1=0 => x=-1
TH2: 3x-1=0 => 3x=1 => x=1/3
b) x^2 - 3x + 2 =0 => x^2 -x - 2x +2 =0 => ( x^2 -x) - (2x -2) =0 => x(x-1) - 2(x-1) =0 => (x-1)(x-2)=0 => x-1=0 hoặc x-2=0
TH1: x-1=0 =>x=1
TH2: x-2=0 => x=2
d)4x^2 - 12x + 5 =0 => 4x^2 - 2x -10x + 5 =0 => ( 4x^2 - 2x) -(10x - 5)=0 => 2x(2x -1 ) - 5(2x-1)=0 => (2x-1)(2x-5)=0 => 2x-1 =0 hoặc 2x-5=0
TH1: 2x-1 =0 => 2x=1 => x=1/2
TH2: 2x-5 =0 => 2x=5 => x=5/2
e)2x^2 + 5x + 3 = 0 =>2x^2 + 3x + 2x +3 =0 => ( 2x^2 + 3x) + (2x +3)=0 => x(2x+3)+(2x+3)=0 =>(2x+3)(x+1)=0 => 2x+3 =0 hoặc x+1=0
TH1: 2X+3=0 => 2x=-3 => x=-3/2
TH2: x+1=0 => x=-1
f) x^2 +x -2=0 => (x-1)(x+2)=0 => x-1=0 hoặc x+2=0
TH1: x-1=0 => x=1
TH2: x+2 =0 => x =-2
g) x^2 - 4x +3 =0 =>(x -3)(x-1)=0 => x-3 =0 hoặc x-1=0
TH1: x-3=0 => x=3
TH2: X-1=0 => x=1
h) 2x^2 + 5x - 3 = 0 => 2x^2 + 6x - x - 3 =0 => ( 2x^2 + 6x)-( x+3)=0=> 2x(x+3)-(x+3)=0 => (x+3)(2x-1)=0 => x+3=0 hoặc 2x-1=0
TH1: x+3=0 => x=-3
TH2: 2x-1=0 => 2x=1 => x=1/2
i) x^2 + 6x - 16 = 0 => (x-2)(x+8)=0 => x-2=0 hoặc x+8=0
TH1: x-2=0 => x=2
TH2: x+8=0 => x=-8
