m²-3m-18=(m-6)(m+3) -xy²+2xy+15x=-x(y^2-2y-15)=-x(y-5)(y+3) 1-a²-2ab-b²=1-(a+b)^2=(1+a+b)(1-a-b)ax-by-bx+ay=ax+ay-(bx+by)=a(x+y)-b(x+y)=(x+y)(a-b)