已知实数xy满足ln(2x 2)
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由x2+xy+y2-2=0得:x2+2xy+y2-2-xy=0,即(x+y)2=2+xy≥0,所以xy≥-2;由x2+xy+y2-2=0得:x2-2xy+y2-2+3xy=0,即(x-y)2=2-3x
x2+2xy+3y2-8y+6=0而,x^2+2xy+3y^2-8y+6=(x+y)^2+2y^2-8y+6=(x+y)^2+2(y-2)^2-2=0(x+y)^2+2(y-2)^2=2所以,|y-2
x^2+y^2=1代表圆C令(x+2)/(y+1)=k题目转化为圆上一点到点A(-2,-1)的斜率的取值范围连接AC,作垂直于AC交圆两点E,F画出图易得到k的取值咯说啥也要满足你E(-1,0),F(
设:S=x-2y,x=S+2y代入x²+y²=1中得:(s+2y)²+y²=15y²+4sy+s²-1=0∵y是实数,∴△≥0(4s)&su
x²+(2-y)x+y²-y+1=0方程有解的条件是:△=b²-4ac≥0→-3y²≥0∴y=0∴x=-1
2x+2xy+2y=4+6根2x2+y2+2x+2xy+2y=10+6根号2(x+y)2+2(x+y)=10+6根号2(x+y+1)2=9+6根号2=(2根号2+1)平方所以x+y+1的绝对值是2根号
已知等式变形得:x2+4xy+4y2-x-2y+14=(x+2y)2-(x+2y)+14=0,即(x+2y-12)2=0,∴x+2y-12=0,则x+2y=12.故答案为:12
分解因式有(x-3y)(2x-y)=0所以有x=3y或2x=y所以x:y=3:1或x:y=1:2
z=3x+y=13(x+2y)/6+5(x-4y)/6当x=5,y=2时取到,z最大值17
x²+y²-xy+x-y/2+1/4=04x²+4y²-4xy+4x-2y+1=04x²-4xy+y²+2(2x-y)+1+3y²
x^2+(2-y)x+y^2-y+1=0这个关于x的二次方程有解b^2-4ac>0-3y^2>0所以y=0x=-1
x²+4xy+4y²+x+2y-6=0(x+2y)²+(x+2y)-6=0(x+2y+3)(x+2y-2)=0(x+2y)=-3或2x+2y=-3时,6/(x+2y)=6
(X+Y+1)^2=X^2+Y^2+1+2XY+2X+2Y=(X^2+Y^2)+2(X+XY+Y)+1=6+2*(2+3√2)+1=6+4+6√2+1=11+6√2
y=-x²+x+3x+y=-x²+2x+3=-x²+2x-1+4=-(x-1)²+4因为-1<0所以当x=1时,x+y的最大值=4
由x2+xy-2y2=0,x2-y2+xy-y2=0,(x+y)(x-y)+(x-y)y=0,(x-y)(x+2y)=0.得x-y=0或者x+2y=0.1)当x-y=0,x=y.(x2+3y+y2)/
x2+4xy+4y2+x+2y-6=0(x+2y)2+(x+2y)-6=0(x+2y+3)(x+2y-2)=0∴x+2y+3=0,x+2y-2=0即:x+2y=-3或2.
解由x2+2y2=6得x2/6+y2/3=1故设x=√6cosa,y=√3sina则x+y=√6cosa+√3sina=3(√6/3cosa+√3/3sina)=3sin(a+θ)由-3≤3sin(a
由x2+y2=1得到的是|xy|=1-1/4=3/4没有用到两边平方吧,你说的两边平方指什么?
再问:лл再问:ʮ�ָ�л
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