1)x²-6x+8=0
x²-2x-4x+8=0
x(x-2)-4(x-2)-0
(x-2)(x-4)=0
x-2=0
x-4=0
x=2
x=4
2)x²-10x+21=0
x²-3x-7x+21=0
x(x-3)7(x-3)=0
(x-3)(x-7)=0
x-3=0
x-7=0
x=3
x=7
3) x² + 12x + 20 = 0
x² + 10x +2x+ 20 = 0
x(x+10)+2(x+10)=0
(x+10)(x+2)=0
x+10=0
x+2=0
x=-10
x=-2
4)x²+6x+5=0
x²+5x+x+5=0
x(x+5)+x+5=0
(x+5)(x+1)=0
x+5-0
x+1=0
x=-5
x=-1
5)x²-4x-12 = 0
x²-2x-6x-12 = 0
x(x+2)6(x+2)=0
(x+2)(x-6)=0
(x+2)(x-6)=0
x+2=0
x-6=0
x=-2
x=6
6)x2-8x-20=0
x2-2x-10x-20=0
x(x+2)10(x+2)=0
(x+2)(x-10)=0
x+2=0
x-10=0
x=-2
x=10
7)x²+2x-35=0
x²+7x-5x-35=0
x(x+7)5(x+7)=0
(x+7)(x-5)=0
x+7=0
x+5=0
x=-7
x=5
8)x²+6x-27 = 0
x²+9x-3x-27 = 0
x(x+9)3(x+9)=0
(x+9)(x-3)=0
x+9=0
x-3=0
x=-9
x=3
9)x² + 9x + 14 = 0
x² + 7x+2x+ 14 = 0
x(x+7)2(x+7)=0
(x+7)(x+2)=0
x+7=0
x+2=0
x=-7
x=-2
10)x²-8x+15=0
x²-3x-5x+15=0
x(x-3)5(x-3)=0
(x-3)(x-5)=0
x-3=0
x-5=0
x=3
x=5
11)x²+x-6=0
x² + 3x-2x -6= 0
x(x+3)2(x+3)=0
(x+3)(x-2)=0
x+3=0
x-2=0
x=-3
x=2
12)x²-3x-28 = 0
x²-4x-7x-28 = 0
x(x+4)7(x+4)=0
(x+4)(x-7)=0
x+4=0
x-7=0
x=-4
x=7
13)x²-7x-18=0
x²-2x-9x-18=0
x(x+2)9(x+2)=0
(x-2)(x-9)=0
x+2=0
x-9=0
x=-2
x=9
14)x²-x-42 = 0
x²-6x-7x-42 = 0
x(x+6)7(x+6)=0
(x+6)(x-7)=0
x+6=0
x-7=0
x=-6
x=7
15)x²+3x-130 = 0
x²+13x-10x-130 = 0
x(x+13)10(x+13)=0
(x+13)(x-10)=0
x+13=0
x-10=0
x=-13
x=10