题目内容：

1.(2x-3y)²-(4y-3x)(3x+4y)
2.(3a²+1/2b)(3a²-1/2b)(9a^4+1/4b²)
3.(x+2)²(x-2)²
4.(3x-5y)²-(3x+5y)²
5.(x+2y-3)(x+2y+3)
6.(a-2b-2c)²