1.x2-3=x2-(√3)2=(x-√3)(x+√3)
2.\(5x^2-7y^2=\left(\sqrt{5}x\right)^2-\left(\sqrt{7}x\right)^2=\left(\sqrt{5}x-\sqrt{7}x\right)\left(\sqrt{5}x+\sqrt{7}x\right)\)
3.x2-2xy+y2-z2+2zt-t2=(x2-2xy+y2)-(z2-2zt+t2)
=(x-y)2-(z-t)2=(x-y-z+t)(x-y+z-t)
4. x3-3x2+3x-1-y3 =(x3-3x2.1+3x.12-13)-y3=(x-1)3-y3
=(x-1-y)[(x-1)2+(x-1)y+y2]
=(x-y-1)(x2-2x+1+xy-y+y2)