解下列各题(1)先化简,再求值:(m+n)2+(m+n)(m-3n)-(2m+n)(2m-n)-(-12
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解下列各题
(1)先化简,再求值:
(m+n)2+(m+n)(m-3n)-(2m+n)(2m-n)-(-
(1)先化简,再求值:
(m+n)2+(m+n)(m-3n)-(2m+n)(2m-n)-(-
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![解下列各题(1)先化简,再求值:(m+n)2+(m+n)(m-3n)-(2m+n)(2m-n)-(-12](/uploads/image/z/15723733-13-3.jpg?t=%E8%A7%A3%E4%B8%8B%E5%88%97%E5%90%84%E9%A2%98%EF%BC%881%EF%BC%89%E5%85%88%E5%8C%96%E7%AE%80%EF%BC%8C%E5%86%8D%E6%B1%82%E5%80%BC%EF%BC%9A%EF%BC%88m%2Bn%EF%BC%892%2B%EF%BC%88m%2Bn%EF%BC%89%EF%BC%88m-3n%EF%BC%89-%EF%BC%882m%2Bn%EF%BC%89%EF%BC%882m-n%EF%BC%89-%EF%BC%88-12)
(1)∵m=(-
1
2)-1,=-2,n=-(π-3.1415)0=-1,
∴(m+n)2+(m+n)(m-3n)-(2m+n)(2m-n)-(-
1
2m2n)2;
=m2+2mn+n2+m2-3mn+mn-3n2-4m2+n2-
1
4m4n2
=-2m2-n2-
1
4m4n2
=-2×(-2)2-(-1)2-
1
4×(-2)4×(-1)2
=-13;
(2)把x=-1,y=-2代入方程组
(m+1)x−(n−2)y=11
mx+(n+3)y=7得:
−m−1+2n−4=11
−m−2n−6=7,
解得:
m=−
29
2
n=
3
4;
(3)原式=-
1
4x(x2-4xy+4y2)
=-
1
2)-1,=-2,n=-(π-3.1415)0=-1,
∴(m+n)2+(m+n)(m-3n)-(2m+n)(2m-n)-(-
1
2m2n)2;
=m2+2mn+n2+m2-3mn+mn-3n2-4m2+n2-
1
4m4n2
=-2m2-n2-
1
4m4n2
=-2×(-2)2-(-1)2-
1
4×(-2)4×(-1)2
=-13;
(2)把x=-1,y=-2代入方程组
(m+1)x−(n−2)y=11
mx+(n+3)y=7得:
−m−1+2n−4=11
−m−2n−6=7,
解得:
m=−
29
2
n=
3
4;
(3)原式=-
1
4x(x2-4xy+4y2)
=-
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