因式分解1.4(x+5)(x+6)(x+10)(x+12)-3x^22.a^4+b^4+c^4-2a^2b^2-2a^2

4.
2a^3+2a^2+2a+a^4+a^2+1
=(a^4+2a^2+1)+(2a^3+2a)+a^2
=(a^2+1)^2+2a(a^2+1)+a^2
=(a^2+1+a)^2
5.
(1+y)^2-2x^2(1+y^2)+x^4(1-y)^2
=(1+y)^2+2(1+y)x^2(1+y)+x^4(1-y)^2-2(1+y)x^2(1-y)-2x^2(1+y^2)
=[(1+y)+x^2(1-y)]^2-2(1+y)x^2(1-y)-2x^2(1+y^2)
=[(1+y)+x^2(1-y)]^2-(2x)^2
=[(1+y)+x^2(1-y)+2x]·[(1+y)+x^2(1-y)-2x]
=(x^2-x^2y+2x+y+1)(x^2-x^2y-2x+y+1)
=[(x+1)^2-y(x^2-1)][(x-1)^2-y(x^2-1)]
=(x+1)(x+1-xy+y)(x-1)(x-1-xy-y)