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(x+2)(x-2)-(x-2)^2 (x-y-1)^2 (3a-b+c)(3a+b-c)

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/11/08 20:58:28
(x+2)(x-2)-(x-2)^2 (x-y-1)^2 (3a-b+c)(3a+b-c)
(x+2)(x-2)-(x-2)^2
(x-y-1)^2
(3a-b+c)(3a+b-c)
(m-n)^2(m+n)^2
(x+2)(x-2)-(x-2)^2=(x-2)[(x+2)-(x-2)]=4(x-2)=4x-8
(x-y-1)^2=[(x-y)-1)]^2=(x-y)^2+1-2(x-y)=x^2+y^2-2xy+1-2x+2y=x^2+y^2-2xy-2x+2y+1
(3a-b+c)(3a+b-c)=[3a-(b-c)][3a+(b-c)]=9a^2-(b-c)^2=9a^2-(b^2+c^2-2bc)
=9a^2-b^2-c^2+2bc
(m-n)^2(m+n)^2=[(m-n)(m+n)]^2=(m^2-n^2)^2=m^4+n^4-2m^2 n^2