(x²-4x)+x-4=0
x(x-4)+(x-4)=0
(x-4)(x+1)=0
x-4=0 x+1=0
x=4 x=-1
(x²+7x)-4x-28=0
x(x+7)-4(x+7)=0
(x+7)(x-4)=0
x+7=0 x-4=0
x=-7 x=4
5x²-10x+(x-2)=0
5x(x-2)+(x-2)=0
(x-2)(5x+1)
x-2=0 5x+1=0
x=2 5x=-1
x=-1/5
3x²+12x-(x+4)=0
3x(x+4)-(x+4)=0
(x+4)(3x-1)=0
x+4=0 3x-1=0
x=-4 3x=1
x=1/3