已知A＝x的平方-2xy,b＝y的平方 xy,求2a-3b.-搜答案-百度作业网

1、已知A＝4x的平方-4xy+y的平方,B=x的平方+xy-5y的平方3A-B=12x²-12xy+3y²-x²-xy+5y²=11x²-13xy+

A+B=2x²-3xy+y²+x²+2xy-3y²=3x²-xy-2y²A-2B=2x²-3xy+y²-2（x²

3A－6B=3(-2x的平方+4xy-2x-3)-6(﹣x的平方＋xy＋2)=-6x²+12xy-6x-9+6x²-6xy-12=（6y-6)x-21∵与x无关∴6y-6=0∴y=

C=-(A+B)=-(2x^2+3xy-2x+(-)x^2+xy-1)=-x^2-4xy+2x+2x^2表示x的平方

错了,A=4X²-4XY+2Y²原式=3A-2B-2A-B=A-3B=4X²-4XY+2Y²-3X²-3XY+15Y²=X²-7X

A=2x^2-3xy+2y^2B=2x^2+xy-3y^2C=x^2-xy-2y^2A-(B-(C-(A+B)))=A-(B-(C-A-B))=A-(B-C+A+B)=A-B+C-A-B=C-2B=(

把c用ab表示出来.然后在减a.就是简单的运算.

2A-3B=16x²y-12xy²-6xy-21xy²+6xy-15x²y=x²y-33xy²

∵A=4x²-4xy+y²B=x²+xy-5y²∴（3A-2B)-(2A+B)=3A-2B-2A-B=A-3B=4x²-4xy+y²-3(x

2A-3B=2·(3x²-xy+y²)-3·(2x²-3xy-2y²)=7xy+8y²B-A-2C=(3x³-2x+5)-(2x³

解题思路：题不完整，请补充解题过程：.最终答案：略

由A=5x*2y-3xy*2+4xy,B=7xy*2-2xy+x*2y得,A+B=6x*2y+4xy*2+2xy则,所求的式子可转化为-0.5x(6x*2y+4xy*2+2xy)-5x*2y-3xy*

a-2b=(5x²y-3xy²+4xy)-2(7xy²-2xy+x²y)=5x²y-3xy²+4xy-14xy²+4xy-2x&#

A=5x^2y-3xy^2+4xyB=7xy^2-2xy+x^2y2C=-A-B2C-2A=-3A-B=-15x^2y+9xy^2-12xy-7xy^2+2xy-x^2y=-16x^2y+2xy^2-

4x的平方+8xy+9y的平方=4x的平方+2xy+9y的平方+6xy=2a+3

2x^2+xy=a,(1)3y^2-2xy=b(2)(1)*2-(2)*3得到4x^2-8xy-9y^2=2a-3b再问：*号是？再答：相乘

A-B=2x^2-3xy+2y^2-(2x^2+xy-3y^2)=2x^2-3xy+2y^2-2x^2-xy+3y^2=2x^2-2x^2-3xy-xy+2y^2+3y^2=-4xy+5y^2

A=5x^2y-3xy^2+4xyB=7xy^2-2xy+x^2y2C=-A-B2C-2A=-3A-B=-15x^2y+9xy^2-12xy-7xy^2+2xy-x^2y=-16x^2y+2xy^2-