A.x+5y=2,xy=7 B.2x+1/y=1,3x-4y=0 C.3x=5y,x/4+y/3=4/3 以上三组哪组属于二元一次方程组

已知A=5x²y-3xy²+4xy；B=7xy²-2xy+x²y,且x+y=2,x-y=0,化简求-1/2（A+B)-A. 因式分解（x+y-2xy)(x+y-2)+(xy-1)^2设x+y=a,xy=b, 已知A=8x^2y-6xy^2-3xy,B=7xy^2-2xy+5x^2y求A-B 已知A=5x^+2xy-4y^,B=-x^-4xy+y^,C=x^-xy+3y^其中xy满足|2x+1|+(y-4)^=0,就A-2B+C已知A=5x^+2xy-4y^,B=-x^-4xy+y^,C=x^-xy+3y^其中xy满足|2x+1|+（y-4)^=0,求A-2B+C-2B+C的值 -4x^2y-8xy^2+2x^2y-3xy^2 合并同类项-4x^2y-8xy^2+2x^2y-3xy^2 3x^2-1-2x-5+3x-x^2 -0.8a^2b-6ab-1.2a^b+5ab+a^2b 5yx-3x^2y-7xy^2+6xy-12xy+7xy^2+8x^2y 合并同类项 求代数式1/2(a-b)^2+1/4(a+b)-1/3(a-b)^2-1/5(a+b)的值,其中a=-1 b=1/2. 如果x^ 已知A=5x^2y-3xy^2+4xy,B=7xy^2-2xy+x^2y.①求A-2B;②求-1/2(A+B)-A. 1.(a^2+ab+b^2)(a^2-ab+b^2)2.(7x-6y)^2+2(7x-6y)(7x+6y)+(7x+6y)^2化简求值1.(2x+y)(2x-y)+(x+y)^2-2(2x^2-xy)其中x=1,y=-1/42.已知x=6.61,y=-3.39.求(x-y)(x^2+3xy+y^2)-5xy*(x-y)的值 已知A=2x²-5xy+2y²+x-2y,B=x²-5/2xy+y²-2x+y,且A-2B=3a,|x-a|+(y-1)²=0 已知6x^2-7xy-3y^2+14x+y+a=(2x-3y+b)(3x+y+1),则a=?,b=? 已知:6x²-7xy-3y²+14x+y+a=(2x-3y+b)(3x+y+1)求a,b的值 已知:6x²-7xy-3y²+14x+y+a=(2x-3y+b)(3x+y+1)求a,b的值 (1)(x+y)^2-(x+y)^3(2)(x-y)-(x-y)^3(3)(x-y)^2-(y-x)^3(4)2(x-y)-3(y-x)^2(5)4ab(a=b)^2-6a^2b(a+b)(6)(x+y)^2(x-y)+(x+y)(x-y)^2(7)2a(a-3)^2-6a^2(3-a)+8a(a-3)(8)24xy^2z^2(x+y-z)-32xyz(z-x-y)^2+8xy(z-x-y)(9)(a-b)(b-a)^n(b-a)^2n-1 [两解）（10）2^2=3,2^b 已知a=x^+xy+y^ b=-3xy-x^求2A-3B 已知A=x^3+3x^2y-5xy^2+6y^3-1,B=y^3+2xy^2+x^2y-2x^3+2,C=x^3-4x^2y+3xy^2-7y^3+1,求证A+B+C的值与x,y无关 已知A=x^3+3x^2y-5xy^2+6y^3-1,B=y^3+2xy^2+x^2y-2x^3+2,C=x^3-4x^2y+3xy^2-7y^3+1,求证A+B+C的值与x,y无关 若A=4x^2-4xy+y^2 B=x^2+xy-5y^2求 (1)A+B (2)B-3A 两个数学计算.a/b-(a-b)/b=x^2+xy/（x-y）÷xy/（x-y） 已知A=4x^2-4xy+y^2,B=x^2+xy-5y^2.求：（1）A-3B(2)3A+B