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-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-36y²

3.(x+4y)(x-9y)
=（x+4y)(x-4y-5y）
=（x+4y）[(x-4y)-5y]
=（x+4y）²-5y(x+4y)
=(x²+8xy+16y²）-（5xy+20y²）
=x²+3xy-4y²

4. (-6y-x)(6y-x)
=[-(6y+x)](6y-x)
=-(6y+x)(6y-x)
=-(36²-x²)
=x²-36y²

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) =36x