如题所述
第1个回答 2011-08-22
1、
(m-n)^2+mn=m^2-mn+n^2
故m^2-mn+n^2=7^2+(-12)=37
2、
(x-2y-3)(x+2y-3)
=[(x-3)-2y][(x-3)+2y]
=(x-3)^2-(2y)^
=x^2-6x+9-4y^2
希望可以采纳，非常感谢！
(m-n)^2+mn=m^2-mn+n^2
故m^2-mn+n^2=7^2+(-12)=37
2、
(x-2y-3)(x+2y-3)
=[(x-3)-2y][(x-3)+2y]
=(x-3)^2-(2y)^
=x^2-6x+9-4y^2
希望可以采纳，非常感谢！
第2个回答 2011-08-22
1、m^2-mn+n^2=m^2-2mn+n^2+mn
=（m-n）^2+mn
=49-12
=37
2、(x-2y-3)(x+2y-3)=[(x-3)-2y][(x-3)+2y]
=(x-3)^2-4y^2
=x^2-6x+9-4y^2本回答被提问者采纳
=（m-n）^2+mn
=49-12
=37
2、(x-2y-3)(x+2y-3)=[(x-3)-2y][(x-3)+2y]
=(x-3)^2-4y^2
=x^2-6x+9-4y^2本回答被提问者采纳
第3个回答 2011-08-22
m^2-mn+n^2
=m^2-2mn+n^2+mn
=(m-n)^2+mn
=49-12
=37
=m^2-2mn+n^2+mn
=(m-n)^2+mn
=49-12
=37
第4个回答 2011-08-22
m^2-mn+n^2
=(m-n)^2+mn
=7^2-12
=37
(x-2y-3)(x+2y-3)
=[(x-3)-2y][(x-3)+2y]
=(x-3)^2-4y^2
=x^2-6x+9-4y^2
=(m-n)^2+mn
=7^2-12
=37
(x-2y-3)(x+2y-3)
=[(x-3)-2y][(x-3)+2y]
=(x-3)^2-4y^2
=x^2-6x+9-4y^2
