已知(x y-1)2与|x 2|互为相反数
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1.3A+6B=15xy-6x-9=(15y-6)x-9与X值无关,则X的系数等与0此时X取什么值(15y-6)x都为0则Y=6/152.设这种上衣有x件500÷(1+25%)x×(1+15%)=69
x2-xy=-3①,2xy-y2=-8②,①×2+②×3得:2x2-2xy+6xy-3y2=-6-24=-30,则2x2+4xy-3y2=-30.
∵2(x2+xy)-3(xy+y2)=2x2-xy-3y2,∴2x2-xy-3y2=2×3-3×(-2)=12.故选A.
已知│x-y+1│与x2+8x+16互为相反数,求x2+2xy+y2的值.x-y+1=0;(1)(x+4)=0;x=-4;y=-4+1=-3;∴x2+2xy+y2=(x+y)²=(-4-3)
∵|x-y+1|与x2+8x+16互为相反数,∴|x-y+1|与(x+4)2互为相反数,即|x-y+1|+(x+4)2=0,∴x-y+1=0,x+4=0,解得x=-4,y=-3.当x=-4,y=-3时
∵A=2x2+3xy-2x-1,B=-x2+xy-1,∴3A=3(2x2+3xy-2x-1)=6x2+9xy-6x-3,∴6B=6(-x2+xy-1)=-6x2+6xy-6,∴3A+6B=(6x2+9
x2-y2=(x2-xy)+(xy-y2)=21-12=9;x2-2xy+y2=(x2-xy)-(xy-y2)=21+12=33.
(1)A-2B=2x2+3xy+2y-1-2(x2−xy+x−12)=2x2+3xy+2y-1-2x2+2xy-2x+1=5xy+2y-2x,当x=y=-2时,A-2B=5xy+2y-2x=5×(-2
X2+xy-(xy+y2)=4-12x2+xy-xy-y2=-8x2-y2=-8x2+xy+xy+y2=4+12x2+2xy+y2=16
解题思路:完全平方公式解题过程:varSWOC={};SWOC.tip=false;try{SWOCX2.OpenFile("http://dayi.prcedu.com/include/readq.
∵x2+xy=5,xy+y2=-1,∴(x2+xy)-(xy+y2)=x2+xy-xy-y2=x2-y2=5-(-1)=6.故填:6
有x2+xy=3可得,2x2+2xy=6 (1),有xy+y2=-2得,3xy+3y2=-6 (2),根据分析,(1)-(2)可得,2x2-xy-3y2=6-(-6)=
(1)∵A=2x2+3xy+2y-1,B=x2-xy+x-12,x-y=-1,xy=1,∴A-2B=(2x2+3xy+2y-1)-2(x2-xy+x-12)=2x2+3xy+2y-1-2x2+2xy-
A-2B=2x2+3xy+2x-1-2(x2+xy+3x-2)=xy-4x-5=(y-4)x-5A-2B与x无关y-4=0y=4回答人的补充2010-10-2822:42设4月份张军手机费用为A,小灵
2x²-xy-3y²=2x²+2xy-3xy-3y²=2(x²+xy)-3(xy+y²)已知x²+xy=3,xy+y²=
0.X^2+XY=3;(1)XY+Y^2=2;(2)2*(1)-3*(2)=2*X^2-XY-3*Y^2=2*3-3*2=0
49(x-2y-5)*2
(1)|x-y+1|≥0,x^2+8x+16=(x+4)^2≥0两者互为相反数,所以|x-y+1|=x^2+8x+16=0x-y+1=0,x+4=0,所以x=-4,y=-3x2+2xy+y2=(x+y
因为x²+4y²+x²y²-6xy+1=0(x²-4xy+4y²)+(x²y²-2xy+1)=0(x-2y)²