-8x^4+32x^2=-8x^2*(x^2-4)=-8x^2*(x+2)(x-2)
10x^3*y+5x^2*y-15x^2*y^2=5x^2*y(2x+1-3y)
m^2*n+14m*n+49n=n(m^2+14m+49)=n(m+7)^2
x^2-(y+5)^2=[x+(y+5)][x-(y+5)]=(x+y+5)(x-y-5)