已知(x y)的²=1,(x-y)的²=17
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原式=(y-x)/xy=-xy/xy=-1
移项,x=y+xy:同除y得x/y=1+x;同除X得1/y=1/x+1;移项1/x-1/y=-1
1/x+1/y=3∴x+y=3xy3x-2xy+3y/x+xy+y=[3(x+y)-2xy]/[(x+y)+xy]=(9xy-2xy)/(3xy+xy)=7/4
代入方法:分母:3x-3xy+3y=3(x+y)-3xy=3•(3xy)-3xy=9xy-3xy=6xy分子:x+xy+y=x+y+xy=3xy+xy=4xy所以原式=6xy/4xy=3/
已知1/x-1/y=3,应该是1/x+1/y=3,[按原式得不出结果!]如此,则3xy=x+y(3x-xy+3y)/(x+xy+y)=2
1/x-1/y=(y-x)/xy=-3y=x=-3xyx-y=3xy所以原式=[5(x-y)+xy]/(x-y)-xy]=[5(3xy)+xy]/[(3xy)-xy]=16xy/2xy=8
令F(XY)=1/XY+XY,当XY=1的时候,F(XY)=2,最小.(可由函数图形象得出).XY趋于正无穷大的时候F(XY)趋于正无穷大,XY无限趋于零的时候F(XY)趋于正无穷大.所以XY越接近1
=-x-(2y-2+3x)+2(x+4)=-x-2y+2-3x+2x+8=-4x-2y+10
首先化简通分1/x+1/y=5得:(x+y)/xy=5即有x+y=5xy将要求的分式化简:3x+xy+3y/x-2xy+y=3x+3y+xy/x+y-2xy(根据加法交换律)=3(x+y)+xy/(x
因为1/x+1/y=3所以x+y=3xy所以x+xy+y/2x-3xy+2y=(3xy+xy)/(6xy-3xy)=4xy/3xy=4/3
1/x+1/y=5(x+y)/x*y=5x+y=5*x*yx+2xy+y=x+y+2xy=5xy+2xy=7xy2x-3xy+2y=10xy-3xy=7xy(x+2xy+y)/(2x-3xy+2y)=
1/x-1/y=3(y-x)/xy=3y-x=3xyx-y=-3xy(5x+xy-5y)/(x-xy-y)=[5(x-y)+xy][(x-y)-xy]=(-15xy+xy)/(-3xy-xy)=-14
(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)=-6xy+3x-3y=-6×(-2)+3×1=15
答:x+y=-1,xy=-2-5(x+y)+(x-y)+x(xy+y)=-5x-5y+x-y+xy(x+1)=-4x-6y+(-2)(x+1)=-4x-6y-2x-2=-6x-6y-2=-6(x+y)
5xy+4x+7y+6x-3xy-4xy+3y=5xy-3xy-4xy+4x+6x+7y+3y=(5-3-4)xy+(4+6)x+(7+3)y=-2xy+10x+10y=-2xy+10(x+y)因为x
是求(3x+xy+3y)/(x-xy+y)吧?(3x+xy+3y)/(x-xy+y)上下同除以xy=(3/y+1+3/x)/(1/y-1+1/x)=[3(1/x+1/y)+1]/(1/x+1/y-1)
-5(x+y)+(x-y)+2(xy+y)=-5x-5y+x-y+2xy+2y=-4x-4y+2xy=-4(x+y)+2xy=-4×(-1)+2×(-2)=4+(-4)=0你有问题也可以在这里向我提问
解题思路::∵x+y=0,x+13y=1,解得x=1/12,y=-1/12∴x²+12xy+13y²=1/144-1/12+13/144=14/144-1/12=2/144=1/72解题过程:已知x+
这道题目还是在考察韦达定理的运用用伟大定理求出xy的值再代入代数式否则是求不出来的(x+y)^2=x^2+y^2+2xy=1x^2+y^2=5(x-y)^2=5-2(-2)=9下面分两种情况讨论1x-
(-2xy+2x+3y)-(3xy+2y-2x)-(x+4y+xy)=-2xy+2x+3y-3xy-2y+2x-x-4y-xy=-6xy+3x-3y=-6*(-2)+3*1=15不懂可追问,有帮助请采