解:原试=(X-1)(X+5)(X+1)(X+3)+1
=(X^2+4X-5)(X^2+4X+3)+1
=(X^2+4x)^2-2(x^2+4x)-14
=(x^2+4x-1)^2-15
=(x^2+4x-1+根号15)(X^2+4X-1-根号15)
(x-1)(x+1)(x+3)(x+5)+1
=(x^2+4x+5)(x^2+4x+3)+1
=(x^2+4x)^2+8(x^2+4x)+15+1
=(x^2+4x)^2+8(x^2+4x)+16
=(x^2+4x+4)^2
=(x+2)^4