(1)x^4-xy^3-x^3y-3x²y+3xy²+y^4
=x^4-x^3y+y^4-xy^3-3x²y+3xy²
=x^3(x-y)-y^3(x-y)-3xy(x-y)
=x^3-y^3-3xy
=(x-y)(x²+xy+y²)-3xy
=x²-2xy+y²
=(x-y)²
=1
(2)a²+ 2ab + b² - 2ac - 2bc + c²
=(a+b-c)²
a=1/3m+1
b=2/3m+2
c=m+6
∴a+b+c=m+3-m-6=-3
∴a²+ 2ab + b² - 2ac - 2bc + c²=9
1.x^4 - xy^3 - x^3y - 3x^2y + 3xy^2+y^4=x^4+2x^2y^2+y^4-2x^2y^2- xy^3 - x^3y - 3x^2y + 3xy^2
=(x^2 -y^2)^2 -xy(x-y)^2 -3xy(x-y)
=(x+y)^2 -xy -3xy
=(x+y)^2 - 4xy =(x-y)^2 =1
2. a^2 + 2ab + b^2 - 2ac - 2bc + c^2=(a+b)^2 +(a-c)^2 + (b-c)^2 -a^2- b^2 -C^2
=(a+b+c)(a+b-c) + (a-b-c)(a+b-c) + (b-c-a)(a+b-c)
=(a+b-c)(a+b-c)=(a+b-c)^2
a=1/(3m)+1 ? , b=2/(3m)+2 ?
a =m/3 +1 ? b=2m/3 + 2 ?
这么简单的都要上网问啊?随便拆拆就OK了