因式分解2x2-xy-4y2 4x2+4xy+y2-10x-5y+6 (1-a2)(1-b2)-4ab

(1)
2x^2-xy-4y^2; 无法有理数因式分解,请检查是不是写错了.非要因式分解的话只能是无理数因式分
2x^2-xy-4y^2
=2(x^2-(1/2)yx)-4y^2
=2{[x-(1/4)y]^2-(1/16)y^2}-4y^2
=2[x-(1/4)y]^2-(33/8)y^2
={√2[x-(1/4)y]-[√(33/8)]y}{√2[x-(1/4)y]+[√(33/8)]y}
=[√2x-(√66/4+√2/4)y][√2x+(√66/4-√2/4)y]
=√2{x-[(√33+1)/4]y}*√2{x+[(√33+1)/4]y}
=2{x-[(√33+1)/4]y}{x+[(√33+1)/4]y}
(2)
4x^2+4xy+y^2-10x-5y+6
=(2x+y)^2-5(2x+y)+6
=(2x+y-2)(2x+y-3)
(3)
(1-a^2)(1-b^2)-4ab
=1-b^2-a^2+a^2b^2-4ab
=(-b^2-a^2-2ab)+(1+a^2b^2-2ab)
=-(a+b)^2+(ab-1)^2
=[(ab-1)-(a+b)][(ab-1)+(a+b)]
=(ab-1-a-b)(ab-1+a+b)

是2x2-xy-4y2吧？

我试做了一下：(1)我没能做出来，或是请您确定一下题目没错
(2)4x2+4xy+y2-10x-5y+6=(2x+y)2-5(2x+y)+6=(2x+y-2)（2x+y－3）
（3）(1-a2)(1-b2)-4ab＝1－a2-b2+a2b2-4ab=1+a2b2-2ab-(a2+b2+2ab)=
(1-ab)2-(a+b)2=(1-ab+a+b)(1-ab-a-b)