先化简再求值(2x的平方y-2xy的平方)-[(-3y的平方-搜答案-智慧作业帮

解3x平方y-[2xy-2(xy-3/2x平方y)+xy]=3x平方y-(2xy-2xy+3x平方y+xy)=3x平方y-(xy+3x平方y)=3x平方y-3x平方y-xy=-xy=-3×(-1/3)

[2x的平方-(x+y)(x-y)][(-x-y)(y-x)+2y的平方]=[2x²-(x²-y²)][(x+y)(x-y)+2y²]=(2x²-x&

x²＋y²＋2x＋4y＋5=0,则(x²＋2x＋1)＋(y²＋4y＋4)=0,即(x＋1)²＋(y＋2)²=0,从而有x=－1,y=－2.【

2(3x的平方+y)-(2x的平方-y)=6x²+2y-2x²+y=4x²+3y=4*(1/2)²+3*(-1)=1-3=-2

2(x^2y+xy)-3(x^2y+4x^2y)-4x^2y=2x^2y+2xy-3x^2y-12x^2y-4x^2y=-17x^2y+2xy把x=-2,y=1/2代入得：原式=-17(-2)^2*2

2（x+y)(x+y)-(x-y)²+（x-y)²=2(x+y)²-[(x-y)²-(x-y)²]=2(x²+2xy+y²)-0=

y是多少原式=(x+y)(x-y)/(x-y)²+x(y+3)/x(y+3)=(x+y)/(x-y)+1=(x+y+x-y)/(x-y)=2x/(x-y)=1/(1/2-y)再问：y=3

(2x-3y)(3y+2x)-(2x-y)²=(2x)²-(3y)²-(4x²-4xy+y²)=4x²-9y²-4x²+

x²-4y²分之x+2y=[(x-2y)(x+2y)]分之x+2y=x-2y分之1=5-2*3.5=-2

2x(x+2y)的平方-(2y+x)的平方(x-2y）=(x+2y)^2(2x-x+2y)=(x+2y)^3=(1/2-2/3)^3=(-1/6)^3=-1/216你能明白,赞同

原式=2x²+4xy+2y²-4xy-2y²+4y-x²+4=x²+4y+4把x=√2,y=-2代入得：原式=2-8+4=-2

x=1+√2,y=1-√2x+y=2x-y=2√2[（1/（x-y)+1/(x+y)]-【2y/（x的平方-2xy+y的平方）】=[（x+y+x-y/（x-y)(x+y)]-【2y/（x-y）^2】=

再问：最后一个是y的平方你写错了再问：最后一个是y的平方你写错了再答：你的题目打的是立方？？？

解(x-y)(x+y)-(x-2y)²+x(3x-5y)-(x-y)(x-2y)=(x²-y²)-(x²-4xy+4y²)+(3x²-5xy

题目有错x²+y²+2x+2y+5=0还是下面二个中的一个x²+y²+4x+2y+5=0x²+y²+2x+4y+5=0原式=（2x-y)[(

X平方+Y平方-2X+4Y+5=0=>(x-1)^2+(y+2)^2=0=>x=1,y=-2（2x+y）（2x+y)-(2x-y)平方=8xy=-16

(1)(x²-y²)/(x²-2xy+y²)=(x-y)(x+y)/(x-y)²=(x+y)/(x-y)x²＋y²－2x－6y＋1

x+1/2=0,y-1=0x=-1/2,y=1原式=4x²y-(6xy-8xy+4-x²y)+1=4x²y-(-2xy+4-x²y)+1=4x²y+2

但是-1的平方不应该得-1么-1的平方=(-1)*(-1)=1负负得正,明白不?

原式=(x²-4y²-x²-4xy-4y²)×(2/y)=(-8y²-4xy)×(2/y)=-16y-8x=-4+8=4