A＝4X²-5XY+Y²,B＝X²+3XY-5Y,求A-2B的值-搜答案-搜狗做题网

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=4X²-4XY+Y²,B=X²+XY-5Y²　∴A-2B=4X²-4XY+Y²-2(X²+XY-5Y²)　　=4X

A=4x²+2xy+y²,B=x²+xy-5y²,A-2B=4x²+2xy+y²-2(x²+xy-5y²)=4X^2+6

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

再答：做这种题要有耐心，记得评价哦

1）2A－B=2（3x²+3y²－5xy）-（2xy－3y²+4x²）=6x²+6y²-10xy-2xy+3y²-4x²

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

A-2B=(4x²+xy+y²)-2(x²+xy-5y²)=4x²+xy+y²-2x²-2xy+10y²=2x²

已知A=4x²-4xy+y²,B=x²+xy-5y²则,A-3B=4x^2-4xy+y^2-3(x^2+xy-5y^2)=4x^2-4xy+y^2-3x^2-3

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

∵|x-1|+（y+3）²=0,|x-1|≥0,（y+3）²≥0；∴x=1,y=-3,∵A＝3x²y-xy²,B=xy-3x²y,∴A-B＝3x

A+B+C=(x+3xy-5xy+6y-1)+(y+2xy+xy-2x+2)+(x-4xy+3xy-7y+1)=(x-2x+x)+(6y+y-7y)+(3xy+xy-4xy)+(-5xy+2xy+3x

因为|2x+1|+(y-4)^=0所以x=-1/2,y=4其余的该会了吧

已知A=5x^2y-3xy^2+4xy,B=7xy^2-2xy+x^2y.（1）求A-2B的值A-2B=5x^2y-3xy^2+4xy-2*(7xy^2-2xy+x^2y)=5x^2y-3xy^2+4

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-

一、x>0,y>0,a＝x+y,b＝√（x²+xy+y²),c=m√xy求是否存在正数m,使对任意正数x,y可便a,b,c为三角形的三边构成三角形,求m.【解答】：①∵a^2=x^

①：A=5x²y-3xy²+4xy=xy（5x-3y+4）B=7xy²-2xy+x²y=xy（7y-2+x）A-2B=xy（5x-3y+4）-2[xy（7y-2

A=4X^2-4XY+Y^2,.(1)B=X^2+XY-5Y^2.(2).(2)*4+,.(1)A+4B=8X^2-19Y^28X^2-19Y^2=A+4B4X^2-3XY=1,X^2-4Y^2=-3

4B=4X²-4XY+20Y²A-4B=4X²-4XY+Y²-（4X²-4XY+20Y²）=﹣19Y²

A=4x²-4xy+y²,B=x²+xy-5y²A+3B=(4x²-4xy+y²)+3(x²+xy-5y²)=4x