求代数式-(3 2x-1 3y的平方) 1 2x.-搜答案-搜搜考试网

x-8>=08-x>=0∴x=8把x=8代入Y=根号X-8+根号8-X在加18得y=18X-Y=18-8=10

（Y+1)^-(Y^-4X)=y*y+2y+1-y*y+4x=2y+4x+1=2(y+2x)+1把y+2x=1代入,得：2*1+1=3所以原代数式的值为3.

-x^2-y^2+4x-6y+13=-(x^2+y^2-4x+6y)+13=-[(x^2-4x+4)+(y^2+6x+9)-13]+13=-[(x-2)^2+(y+3)^2]+26∵(x-2)^2≥0

18

x^2+y^2+2x+4y=-5(题目错了吧?)x^2+2x+1+y^2+4y+4-5=-5(x+1)^2+(y+2)^2=0x=-1,y=-2,所以：x/y+y/x=1/2+2=2.5

因为x+y=5,所以（x+y)^2=x^2+y^2+2xy=25（1）将x^2+y^2=13代入（1）式求得xy=6x^3y+2x^2y^2+xy^3=xy(x^2+2xy+y^2)=6(x+y)^2

x=1/3y=1/2x-(x+y）+（x+2y)-(x+3y)+...-(x+13y)=6y-13y=-7y=-7/2=-3.5

7-x+y-(y-x)=7-(x-y)+(x-y)……（这步添括号,y-x=-(x-y),代入x-y=3）=7-3+3=77^2=49（7的平方等于49）

已知y/x=2,则求代数式x+y/4x-5y的值分子分母同除以xy；=(1+y/x)/(4-5y/x)=(1+2)/(4-5×2)=3/(-6)=-1/2;您好,很高兴为您解答,skyhunter00

原式=1/2×2x-y/x+y+2x-y/6x-3y=1/2+1/3=5/6

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)

由x²+y²+2x-4y+13=（x²+2x+1）+（y²-4y+4）+8=（x+1）²+（y-2)²+8,当x=-1,y=2时：x&sup

原式=2X²-4XY+2Y²+3Y²-12Y+12+1=2(X-Y)²+3(Y-2)²+1平方数大于等于0所以2(X-Y)²+3(Y-2)&

因为X-Y=1所以原式=x*1+y*（-1）+2013=x-y+2013=1+2013=2014

7-x+y-(y-x)^2=7-(x-y)-(x-y)^2把x-y=3代入原式=7-3-3^2=-5

X^2Y+2x^2y^2+xy^2=xy(x+y)+2x^2y^2=5xy+2x^2y^2=xy(5+2xy)因为x+y=5,x^2+y^2=13,这两个式子联立方程,得到xy=6,带入上式,得到所求

(x+y)>=0-(x+y)^2

是这样的,x+y=5,x方加y方=13,所以可以求得xy,就是(x+y)的平方等于25,也就是x方+2xy+y方等于25,再用这个试子减x方+y方,剩下2xy=12,代数式x方y+2x方y方+xy方,

7-x+y-(y-x)^2=7-(x-y)-(x-y)^2=7-3-3^2=4-9=-5

原式化简=x＋2y=2011