若x-y=5,-xy=3求(7x 4y xy)
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-xy(x^2y^5-xy^3-y)=-(xy^2)^3+(xy^2)^2+xy^2=-(-2)^3+4-2=8+4-2=10
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
首先化简:原式=7x+4y+xy-5y-6x+6xy=(x-y)+7xy因为,x-y=5,-xy=3所以原式=5-21=-16楼上忘记加负号了~
你好:原式=(7x+4y+xy)-(5y+6x-6xy)……………………把“6”乘进去=7x+4y+xy-5y-6x+6xy=x-y+7xy因为x-y=5,-xy=3所以xy=-3所以,原式=5+7乘
(1)+(2)得x²+2xy+y²+5x+5y=0(x+y)²+5(x+y)=0(x+y)(x+y+5)=0∴x+y=0或x+y=-5
0或-5过程看图再问:你QQ好能给我吗?以后不会的可以问你。再答:本人资料里可以找到
1/x+1/y=5两边乘以xy得y+x=5xy∴x+y=5xy3x+4xy+3y/x+3xy+y=[3(x+y)+4xy]/[(x+y)+3xy]=(15xy+4xy)/(5xy+3xy)=19xy/
x/y+y/x=(x²+y²)/xy=[(x+y)²-2xy]/xy=(x+y)²/xy-2=25/3-2=19/3
(3xy+2)^2+|7-x-y|=0,则3xy+2=0,7-x-y=0,即x+y=7,xy=-2/3(5xy+10y)-[-5x-(4xy-2y+3x)]=5xy+10y-(-5x-4xy+2y-3
先把代数式(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)化简(5XY+4X+7Y)+(6X-3XY)-(4XY-3Y)=5XY+4X+7Y+6X-3XY-4XY+3Y=-2XY+10X+1
最简单的方法就是用特殊值,令x=-2,y=1然后代入所求表达式,求出其值.为-8;另外此内题的另一个解法是变化所求表达式,使它变成关于xy^2的表达式.
(7xy+4x-7y)+(6x-3xy)-(3y+4xy)=7xy+4x-7y+6x-3xy-3y-4xy=10x-10y=10(x-y)=10*3=30
(5xy+4x+7y)+(6x-3xy)-(4xy-3y)=5xy+4x+7y+6x-3xy-4xy+3y=(5xy-3xy-4xy)+(4x+6x)+(7y+3y)=-2xy+10x+10y=-2x
(7x+4y+xy)-6(5/6y+x-xy)=7x+4y+xy-5y-6x+6xy=x-y+7xy=5+7×(-3)=-16
把括号打开7X+4Y+XY-5Y-6X+6XY=X-Y+7XY=5+7*(-3)=-16
(7x+4y+xy)-6(六分之五y+x-xy)=7x+4y+xy-5y-6x+6xy=x-y+10xy把x-y=5和-xy=3代入x-y+10xy=5+10*(-3)=5-30=-25所以原式的值是
得y-x=3xyx-y=-3xy原式=-15xy+2xy/-3xy-4xy=-13/-7=13/7
x²+xy+5y=3……………………①y²+xy+5x=﹣3.………………②①+②得:x²+2xy+y²+5x+5y=0﹙x+y﹚²+5﹙x+y﹚=0
x+y=5xy(2x-3xy+2y)/(x+2xy+y)=[2(x+y)-3xy]/[(x+y)+2xy]=(2×5xy-3xy)/(5xy+2xy)=7xy/7xy=1再问:若x+1/x=3,求(x
x²+y²=7转成x²=7-y²将xy=-2和x²=7-y²代人(5x²-3xy-4y²-11xy-7x²+2