如果x+y等于3,xy等于1,则-5x-搜答案-大师作文网

x=1x+y=0y=-1xy=-1

x²+xy=2xy+y²=-1两式相减得：x²-y²=3两式相加得：x²+2xy+y²=1

1/x-1/y=2y-x=2xyx-y=-2xy(3x+7xy-3y)/(2x-3xy-2y)=[3(x-y)+7xy]/[2(x-y)-3xy]=[-6xy+7xy]/[-4xy-3xy]=xy/[

选B因为：(y+2)^2>=0恒成立|2x-1|>=0恒成立且|2x-1|+(y+2)＾2=0所以2x-1=0x=0.5y+2=0y=-2所以xy=0.5*(-2)=-1选B

是的再答：再问：那可以问一道题吗再问：再问：第三小题再答：再问：ab的值一定吗？若入x等于y呢再答：再答：不好意思啊，没想那么多，十多年没复习了

通分1/x-1/y=(y-x)/xy=3y-x=3xyx-y=-3xy原式=[(x-y)-2xy]/[5(x-y)+3xy]=(-3xy-2xy)/(-15xy+3xy)=-5xy/(-12xy)=5

解析：

将x=7,y=1代入3x-ay=16,2x+by=1521-a=1614+b=15解出a=5b=1代入3（x+y）-a（x-y）=16,2（x+y）+b（x-y）=153(x+y)-5(x-y)=16

(x+y)(x-y)-(x的2次方-3xy)=x²-y²-x²+3xy=3xy-y²=3x2x(-1/2)-(-1/2)²=-3-1/4=-3.25

你传错了吧,怎么无解啊~

x²＋xy＝3………………………①y²＋xy＝－2……………………②①＋②得：x²＋2xy＋y²＝1（x＋y）²＝1x＋y＝±1∴x²＋3x

1/3x²+2/3xy+1/3y²=1/3(x²+2xy+y²)=1/3(x+y)²=1/3×(-6)²=1/3×36=12很高兴为您解答,

如果绝对值X-Y+1+根号（X-3）的平方=0x-y+1=0x-3=0x=3y=4xy=3x4=12

xy+1/xy+y/x+x/y=[(xy)^2+1+x^2+y^2]/(xy)=[(xy)^2-2xy+1+x^2-2xy+y^2+4xy]/(xy)=[(xy-1)^2+(x-y)^2+4xy]/(

1/x-1/y=(y-x)/xy=3所以y-x=3xy代入后面的公式得(-5xy)/(-9xy)=5/9

3x²-xy+y²=101-xy+4y²=421-2得3x²-3y²=6x²-y²=2选B

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

如果x的平方加xy等于2,y的平方加x的y等于-1,则x的平方-y的平方=?x的平方加2xy加y的平方等于多少?x²+xy=2y²+xy=-1x²+xy-y²-