(c-3)^2-4x^2=(c-3-2x)(c-3+2x)
y^2x+(x+y)+yx^2+4xy+4=yx(y+x)+(x+y)+4(xy+1)=(x+y)(xy+1)+4(xy+1)=(xy+1)(x+y+4)
(c-3)^2-4x^2=(c-3-2x)(c-3+2x)
y^2x+(x+y)+yx^2+4xy+4=yx(y+x)+(x+y)+4(xy+1)=(x+y)(xy+1)+4(xy+1)=(xy+1)(x+y+4)