(2a^2-a)(2a^2-a-9)+18 (x^2-x)^2-14x^2+14x+24 (x+1)(x+3)(x+5)(x+7)-9

1.解：(2a^2-a)(2a^2-a-9)+18
=(2a^2-a)^2-9(2a^2-a)+18
=(2a^2-a-3)(2a^2-a-6)
=(2a-3)(a+1)(2a+3)(a-2)
=(a+1)(a-2)(2a-3)(2a+3).

2.解：(x^2-x)^2-14x^2+14x+24
=(x^2-x)^2-14（x^2 -x) +24
=(x^2-x -2)(x^2-x -12)
=(x +1)(x -2)(x +3)(x -4)

3.解：(x+1)*(x+3)*(x+5)*(x+7)-9
=[(x+1)*(x+7)]*[(x+5)*(x+3)]-9
=(x^2+8x+7)(x^2+8x+15)-9
=[(x^2+8x+11)-4][(x^2+8x+11)+4]-9
=(x^2+8x+11)^2-4^2-9
=(x^2+8x+11)^2-25
=(x^2+8x+6)(x^2+8x+16)
=(x^2+8x+6)(x+4)^2