作业帮3a(x y) (a-b)(x y)
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/11 02:54:21
∵A=x2+xy+y2，B=-3xy-x2∴2A-3B=2（x2+xy+y2）-3（-3xy-x2）=2x2+2xy+2y2+9xy+3x2=5x2+11xy+2y2．
A+B-3C=08x²y-6xy²-3xy+7xy²-2xy+5x²y-3C=0(13x²y-5xy+xy²)/3=CC-A=(13x&su
A-2B=5x²-3xy²+2xy-2(7xy²-2xy+x²y)=5x²-3xy²+2xy-14xy²+4xy-2x²
∵xy/(a＋b)＝1/15∴a＋b＝15xy同理：b＋c＝17xya＋c＝16xy∴xy/(a＋b＋c)＝xy/[1/2(2a＋2b＋2c)]＝xy/[1/2(a＋b＋b＋c＋a＋c)]＝xy/[1
x^2-3xy+4y^2=(x^2+xy)+4(y^2-xy)=a+4
解2A-[B-(B-A)+2A+B]=2A-[B-B+A+2A+B]=2A-(B+3A)=-B-A=-(x²+2xy+y²-3)-(x²-2xy+y)=-x²-
把c用ab表示出来.然后在减a.就是简单的运算.
解∵2x²+xy=a∴4x方+2xy=2a----------（1）3y²-2xy=b∴9y方-6xy=3b-----------（2）（1）-（2）得：4x方+8xy-9y方=2
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+B=(x²-3xy+y²)+(2x²+xy-9y²)=x²-3xy+y²+2x²+xy-9y²=3x²-2
解C=(-A-B)/2=-2x^2y+xy-2xy^2C-A=-7x^2y-3xy+xy^2
⑴原式=Y/(14X-Y)⑵原式=1/(a-b)⑶原式=(X+Y)/2⑷4a^3(X-Y)/9.再问：要过程！再答：分子与分母分别分解因式，然后约分。⑴原式=3XY/［3X(14-Y)］=Y/(14-
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-
4x²+8xy+9y²=2x²+2x²+xy+xy+6xy+9y²=2a+9y²+6xy=2a+3y²+2xy+3y²+
C=3A+3B所以C-2A=3A+3B-2A=A+3B=8x²y-6xy²-3xy+21xy²-6xy+15x²y=23x²y+15xy²-
∵A=8x²y-6xy²-3xy,B=7xy²-2xy+5x²y ∴C=3（A+B) =3(8x²y-6xy²-3xy+7xy²
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
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