计算：1.(-6y+x)(-6y-x) 2.(-6y+x)(6y-x) 3.(x+4y)(x-9y) 4.(-6y-x)(6y-x)

1.(-6y+x)(-6y-x)
=(-6y)²-x²
=36y²-x²
2.(-6y+x)(6y-x)
=-(6y-x)(6y-x)
=-(6y-x)²
=-(36y²-12y+x²)
=-36y²+12y-x²
3.(x+4y)(x-9y)
=x²-9xy+4xy-36y²
=x²-5xy-36y²
4. (-6y-x)(6y-x)
=(-x-6y)(-x+6y)
=(-x)²-(6y)²
=x²-36y²

啊是各提一个负号（6y-x)(6y+x) =36x2-x2 (-6y+x)(6y-x)=-36y2+6xy+6xy+ -x2
(x+4y)(x-9y)=x2-9xy+4xy-36y2=x2-5xy-36y2
(-6y-x)(6y-x)=(x+6y)(x-6y)=x2-36y2

1.(-6y+x)(-6y-x) =[-(6y-x)][-(6y+x)] =(6y-x)(6y+x) =(6y)²-x² =36y²-x² 2.(-6y+x)(6y-x) =[-(6y-x)](6y-x) =-(6y-x)(6y-x) =-[(6y-x)²] =-（36y²-12xy-x²） =x²+12xy-36...