因式分解1.-4(x-2y)的平方+9(x+y)的平方2.x的三次方-x的平方-x+13.a的四次方+a的平方-b的四次

给你一个清晰的过程：
1。-4(x-2y)²+9(x+y)²
=9(x+y)²-4(x-2y)²
=[3(x+y)+2(x-2y)][3(x+y)-2(x-2y)]
=[3x+3y+2x-4y][3x+3y-2x+4y]
=(5x-y)(x+7y)
2。x³-x²-x+1
=(x³-x²)-(x-1)
=x²(x-1)-(x-1)
=(x-1)(x²-1)
=(x-1)(x-1)(x+1)
=(x-1)²(x+1)
3。a^4+a^2-b^4+1/4
=(a^4+a^2+1/4)-b^4
=(a^2+1/2)^2-b^4
=[(a^2+1/2)+b^2][(a^2+1/2)-b^2]
=(a^2+b^2+1/2)(a^2-b^2+1/2)