x^2+x-4x-4=0
x(x+1)-4(x-1)=0
(x+1)(x-4)=0
{x+1=0 =>{x= -1
{x-4=0 =>{x=4
ответ:x1= -1;x2=4.
x²-3x-4=0
x²+x-4x-4=0
x×(x+1)-4(x+1)=0
(x+1)×(x-4)=0
x+1=0
x-4=0
x=-1
x=4
