帮忙做几道因式分解！！！

x^4+1/4y^4=x^4+1/4y^4+x^2y^2-x^2y^2=(x^2+y^2/2)^2-x^2y^2=(x^2+y^2/2+xy)(x^2+y^2/2-xy)

2a^2-b^2-ab+bc+2ac
=(2a+b)(a-b)+c(b+2a)
=(a-b+c)(2a+b)

3x^2+4xy-4y^2+8x-8y-3
=(3x-2y)(x+2y)+8x-8y-3
=(3x-2y-1)(x+2y+3){即把3x-2y,x+2y看成整体,把-3拆成-1,3,再十字交叉得(3x-2y)*3-(x+2y)=8x-8y}
如下
(3x-2y) -1
(x+2y) 3

最后一题目有问题,应为
a(6a+11b+4)+b(3b-1)-2
=6a^2+11ab+3b^2+4a-b-2
=(2a+3b)(3a+b)+4a-b-2
=(2a+3b+2)(3a+b-1)
(2a+3b) 2
(3a+b) -1

x^4+1/4y^4=x^4+1/4y^4+x^2y^2-x^2y^2=(x^2+2/1y^2)-x^2y^2=(x^2+2/1y^2+xy)(x^2+2/1y^2-xy)

2a^2-b^2-ab+bc+2ac
=a^2+(a+b)(a-b)-ab+c(a+b)+ac
=a^2-ab+ac+(a+b)(a-b+c)
=a(a-b+c)+(a+b)(a-b+c)
=(a-b+c)(2a+b)