x＝2,y＝1.5,3x的平方 4y＝几

x^2-y^2=(x+y)(x-y)30=4/3*(x-y)x-y=30*3/4x-y=45/2

由3x+4y-15=0得出y=(15-3x)/4x*x+y*y=x^2+(15-3x)^2/16=(25x^2-90x+225)/16=(x-9)^2*25/16+225/16-25*81/16开口向

2x+2y+z＝0(1)5x+4y-4z＝0(2)(2)-(1)*2得x=6z把x=6z代入（1）得y=-13z/2把x=6z,y=-13z/2代入3x平方-4y平方+5z平方／x平方+6y平方-10

15/16再问：要过程，这位大姐再答：由已知得X=﹣4／3Y，Z=﹣2／3Y，带入可得15／16再问：怎么得出再答：解方程组，①式*4+②式得x=-4/3y,代入①得z=-2/3y,再将x,z代入代数

x+2绝对值+（y-3)的平方＝0则x+2=0,y-3=0则x=-2,y=3则X的绝对值+2=2+2=4xy÷x平方-y的平方=-6÷4-9=-10又2分1

因为|x-3y+6|+(x+2y-1)的平方＝0,两个非负数的和为0,只有两个非负数同时为0.x-3y+6=0,x+2y-1=0.解得：x=-9/5,y=7/5.

(3xy)平方/(-xy)+(x-2y)平方-(x+2y)(x-2y)=-9xy+(x-2y)(x-2y-x-2y)=-9xy+(x-2y)(-4y)=-9xy-4xy+8y²=8y

2(y-x)²-7(x-y)+6(x-y)-3(y-x)²=-(y-x)²-(x-y)=-(x-y)²-(x-y)=-(x-y)[(x-y)+1]=(y-x)(

（x+y）(x+2y)=x²+xy+2xy+2y²=x²+3xy+2y²

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

(x-2y+3z)^2-(x+2y-3z)^2=[x-2y+3z+(x+2y-3z)][x-2y+3z-(x+2y-3z)]=2x*(-4y+6z)=-8xy+12xz

只有当绝对值和平方都等于0时等式才成立,所以：x+2y-3=02x+y=0所以解得x=-1,y=2

3(x-y)²*(y-x)²*2(x-y)=6(x-y)^(2+2+1)=6(x-y)^5再问：需要再详细一点的过程再答：3(x-y)²*(y-x)²*2(x-

|x-3y－6|+(x+2y-1)的平方＝0x-3y-6=0x+2y-1=0即﹛x-3y=6﹙1)x+2y=1(2)(2)-(1)得5y=-5y=-1代入（2）得x-2=1x=3

X+Y=0.2(1)式X+3Y=1(2)式用(2)-(1)得2Y=0.8Y=0.4把Y=0.4代入得X=-0.23（X+2y)^2=1.08

1、y=(x^2-3x+2)e^x,故y'=(x^2-3x+2)'*e^x+(x^2-3x+2)*(e^x)'而显然(x^2-3x+2)'=2x-3,(e^x)'=e^x所以y'=(2x-3)*e^x

1.(2x-3y)^2-(y+3x)(3x-y)=4x^2-12xy+9y^2-(3x+y)(3x-y)=4x^2-12xy+9y^2-9x^2+y^2=10y^2-5x^2-12xy2.[(x-y)

(x+2)^2-(y-3)^2=(x+y)*(x-y)x^2+4x+4-y^2+6y-9=x^2-y^24x+6y-5=0即为所求的方程

3x^2y+2x=4两边乘以-3、得-9x^2y-6x=-12故-6x-9x^2y+2=-12+2=-10

(3x-y)的平方-(2x+y)的平方-5(x-y)=(3x-y+2x+y)(3x-y-2x-y)-5(x-y)=5x(x-2y)-5(x-y)=5x^2-10xy-5x+5y