Question

初中数学题、求答案、急！！！大家帮帮忙！！谢谢各位了！！

因式分解:

①3a^2 x^2 y^2-27a^2 ②(a+3)(a-7)+25 ③81a^4+16b^4-72a^2 b^2

2．计算：①(3x+1)^2(3x-1)^2 ②(x+1)(x^2+1)(x^4+1)(x-1)
③(x-2y+z)(-x+2y+z) ④（a+2b－3c)（a－2b+3c）

【要过程！！！】

Answer 1

①3a^2 x^2 y^2-27a^2
=3a^2(x^2y^2-9)
=3a^2(xy+3)(xy-3)

②(a+3)(a-7)+25
=a^2-4a-21+25
=a^2-4a+4
=(a-2)^2

③81a^4+16b^4-72a^2 b^2
=(9a^2-4b^2)^2
=(3a+2b)^2 (3a-2b)^2

2．计算：
①(3x+1)^2(3x-1)^2
=[(3x+1)(3x-1)]^2
=(9x^2-1)^2
=81x^4-18x^2+1

②(x+1)(x^2+1)(x^4+1)(x-1)
= (x-1)(x+1)(x^2+1)(x^4+1)
=(x^2-1)(x^2+1)(x^4+1)
=(x^4-1)(x^4+1)
=x^8-1

③(x-2y+z)(-x+2y+z)
=[z+(x-2y)][z-(x-2y)]
=z^2-(x-2y)^2
=z^2-x^2+4xy-4y^2

④（a+2b－3c)（a－2b+3c）
=[a+(2b-3a)][a-(2b-3c)]
=a^2-(2b-3c)^2
=a^2-4b^2+12bc-9c^2