计算题要过程

1.（a+b+2c)(a+b-2c) =(a+b)^2-(2c)^2=a^2+2ab+b^2-4c^2
2.(y-3)^2-2(y+2)(y-2) =y^2-6y+9-2(y^2-4)=-y^2-6y+17
3.(2a+1)^2(2a-1)^2 =[(2a+1)(2a-1)]^2=(4a^2-1)^2=16a^4-8a^2+1
4.(x-2y)^2+2(x+2y)(x-2y)+(x+2y)^2
=[(x-2y)+(x+2y)]^2
=(2x)^2=4x^2

一分没有出了4题~太黑了点吧~不想出分的麻烦分开成4个出- -!

1.（a+b+2c)(a+b-2c)
=[(a+b)+2c][(a+b)-2c]
=(a+b)^2-4c^2
=a^2+2ab+b^2-4c^2

2.(y-3)^2-2(y+2)(y-2)
=y^2-6y+9-2y^2+8
=-y^2-6y+17

3.(2a+1)^2(2a-1)^2
=[(2a+1)(2a-1)]^2
=(4a^2-1)^2
=16a^4-8a^2+1

4.(x-2y)^2+2(x+2y)(x-2y)+(x+2y)^2
=(x-2y+x+2y)^2
=(2x)^2
=4x^2