1)
(x+1)(x+2)(x+3)(x+4)-120
=[(x+1)(x+4)][(x+2)(x+3)]-120
=(x^2+5x+4)(x^2+5x+6)-120
=(x^2+5x)^2+10(x^2+5x)+24-120
=(x^2+5x)^2+10(x^2+5x)-96
=[(x^2+5x)+16][(x^2+5x)-6]
=(x^2+5x+16)(x^2+5x-6)
=(x^2+5x+16)(x+6)(x-1)
2)
(x^2+3x-3)(x^2+3x+4）-8
=[(x^2+3x)-3][(x^2+3x)+4]-8
=(x^2+3x)^2+(x^2+3x)-12-8
=(x^2+3x)^2+(x^2+3x)-20
=(x^2+3x+5)(x^2+3x-4)
=(x^2+3x+5)(x+4)(x-1)