xy=(x-5)(y 2)
来源:学生作业帮助网 编辑:作业帮 时间:2024/05/24 11:27:54
原式=[x-y(x-y)2-y(x+y)(x+y)(x-y)]•xyy-1=(1x-y-yx-y)•xyy-1=1-yx-y•xyy-1=-xyx-y.故答案是:-xyx-y.
将x+y=5两边平方得:(x+y)2=x2+2xy+y2=25,把xy=3代入得:x2+y2=19.故答案为:19.
xy/x+y=1/3x+y=3xyx2y2/x2+y2=1/5(xy)²/[(x+y)²-2xy]=1/5(xy)²/[(3xy)²-2xy]=1/5(xy)&
X2+Y2=6(x+y)²-2xy=6又XY=5∴(x+y)²=16x+y=4或x+y=-4
∵x²-2xy-3y²=0∴*(x-3y)(x+y)=0∴x=3y或x=-y(1)2x+y/x-2y当x=3y时,原式=7y/y=7当x=-y时,原式=y/(-3y)=-1/3(2
将x+y=10两边平方得:(x+y)2=x2+2xy+y2=100,将xy=5代入得:x2+y2=90.
:(1)2x2-5x+x2+4x,其中x=-3=3x²-x=3x(-3)²+3=27+3=30(2)(3x2-xy-2y2)-2(x2+xy-2y2),其中x=6,y=-1=3x&
将x+y=5两边平方得:(x+y)2=x2+2xy+y2=25,将xy=6代入得:x2+12+y2=25,则x2+y2=13.故选B.
将x-y=5两边平方得:(x-y)2=25,即x2+y2-2xy=25,把xy=3代入得:x2+y2=31.
(x+y)2=x2+y2+2xy把x+y=5,x2+y2=13,代入上式得52=13+2xy,解得xy=6.
把题写纸上传个图片吧,这样题目有歧义啊
已知2x=3y,求xy/(x^2+y^2)-y^2/(x^2-y^2)的值2x=3y-->x=(3/2)yx^2=(9/4)y^2xy/(x^2+y^2)-y^2/(x^2-y^2)==(3/2)y*
把x+y=5,两边平方得:(x+y)2=x2+y2+2xy=25,将xy=6代入得:x2+y2+12=25,则x2+y2=13.故答案为:13
(x-y)^2=81,x^2+y^2-2xy=81,x^2+y^2=81+2xy=91注:x^为x的平方.
因为x2+y2=5,xy=2所以(x+y)^2=9x+y=+/-3所以1/(1/x+1/y)=xy/(x+y)=+/-2/3
2x2+5xy-3y2=0(2X-Y)(X+3Y)=0==>X=Y或者X=-3YXY不等于0,即X,Y都不等于0所以X:Y=X/Y=1或者-1/3
∵x+y=-5,∴(x+y)2=25,∴x2+2xy+y2=25,∵xy=6,∴x2+y2=25-2xy=25-12=13.故答案为:13.
x²-2xy+y²/x²-y²=(x-y)²/(x-y)(x+y)=(x-y)/(x+y)因为x=3,y=-5,所以(3-(-5))/(3+(-5))
由x2+xy+y2=3得,x^2+y^2=3-xyx^2+y^2≥2xy得,xy≤1所以x^2-xy+y^2=3-2xy≥1等号成立当且仅当x=y=±1
因为x²+4y²+x²y²-6xy+1=0(x²-4xy+4y²)+(x²y²-2xy+1)=0(x-2y)²