初一数学题4道~！都是初一下学期整式运算题~！过程

1
(2x^2)^3-6x^3(x^3+2x^2+x)
=(8x^6)-(6x^6+12x^5+6x^4)
=8x^6-6x^6-12x^5-6x^4
=2x^6-12x^5-6x^4

2
(x+y+z)(x+y-z)
=(x+y)^2 - z^2
=x^2 + y^2 -2xy -z^2

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

4
a^2 (a+1)^2-2(a^2-2a+4)
=a^2[a^2 + 2a +1]-(2a^2-4a+8)
=a^4 + 2a^3 + a^2 - 2a^2 + 4a -8
=a^4 + 2a^3 - a^2 + 4a - 8

小孩子， 好好学习啊，投机取巧是不行滴