1.原式=(x-1)(x-4)-1
2.x^2-2根号2*x-3
=x^2-2根号2*x+（根号2）^2-（根号2）^2-3
=（x-根号2）^2-5
=（x-根号2）^2-（根号5)^2
=(x-根号2+根号5)(x-根号2-根号5)