3 2x=56y那么xy等于多少
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x+y=3,z-y=5,x+z=8(x+y)^2+(z-y)^2+(x+z)^2-2(xy-yz+xz)=x^2+y^2+2xy+z^2-2zy+y^2+x^2+2xz+z^2-2(xy-yz+xz)
x²-5xy+6y²=0,(x-3y)(x-2y)=0x=3y或x=2y(1)当x=3yx+y分之x-y=(3y-y)/(3y+y)=1/2(2)当x=2yx+y分之x-y=(2y
√xy+y分之一+√xy+x分之一=√xy(1/x+1/y)=√xy乘[(x+y)/xy]=√xy(x+y)再问:√xy(1/x+1/y)这一步怎样计算?再答:(1/x+1/y)1/x和1/y通分再问
y²=12y=±√12=±2√3xy=√6×(±2√3)=±2√18=±6√2于是4/xy=4/(±6√2)=±√2/3再问:你4/(±6√2)那里是怎么化简的,可以写下过程吗。。再答:4/
x+y=2,y=2-x,xy=x(2-x)若x=0,2,xy=0若2>x>0,2>xy>0x2,xy
x的三次方y的平方+x的平方y三次方=x²y²(x+y)=(xy)²(x+y)=(-2)²*(-3)=-12
x+y=3-------(1)xy=1--------(2)将(1)平方得x^2+y^2+2xy=9------(3)将(2)乘以2得2xy=2--------(4)将(3)减去(4)得x的平方加上y
xy+(x+y)=8,那么xy=8-(x+y)由基本不等式得:xy≤[(x+y)/2]²所以8-(x+y)≤[(x+y)/2)]²即:(x+y)²+4(x+y)-32≥0
不需要图,很简单的z=xy+u两边对x求导:∂z/∂x=y+∂u/∂x,两边对y求导:∂²z/(∂x∂y)
x²+xy=3………………………①y²+xy=-2……………………②①+②得:x²+2xy+y²=1(x+y)²=1x+y=±1∴x²+3x
你先设x/y=k,即x=yk所以原式=3k^2y^2+ky^2-4y^2=0即y^2(3k^2+k-4)=0因为y不能等于0,所以^2不等于0即3k^2+k-4=0得k=1(x不等于y,舍去),K=-
2(x+xy)-[(xy-3y)-x]-(-xy)=2x+2xy-xy+3y+x+xy=3x+3y+2xy=3(x+y)+2xy=3*(-2)+2*3=0
前面,22,后面8再问:有再问:过程吗?再答:
1/x-1/y=3则x-y=-3xyx-3xy-y/2x-xy-2y=(-3xy-3xy)/(-6xy-xy)=6/7
1/x-1/y=2(y-x)/xy=2y-x=2xy(3x+5xy-3y)/(x-xy-y)=[5xy-3(y-x)]/[-xy-(y-x)]=(5xy-6xy)/(-xy-2xy)=-xy/-3xy
x^2+2xy+y^2=(x^2+xy)+(xy+y^2)=2+7=9
(x+y)²=x²+2xy+y²=(x²-2xy+y²)+4xy=(x-y)²+4xy=49所以x+y=±7x²y+xy²
2A-3B=2(3x²-xy+y²)-3(2x²-3xy-2y²)=6x²-2xy+2y²-6x²+9xy+6y²=7x