X 2 Y 1 3=3 3X-2Y=8

y'=2-x的-2次方×8y'=2-8x^（-2）y′=2-8/x²

(4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=4x-2y-z-5x[6y-(x+y)]+x-(3y-10z)=4x-2y-z-30xy+5x²+5xy+x-3

（x+2y)(x-2y)-(2y-x)(-2x-y)=（x+2y)(x-2y)+(x-2y)(-2x-y)=(x-2y）[(x+2y)+(-2x-y)]=(x-2y)(-x+y)代入x=8y=-8=-

[(x+2y)(x-2y)-(x-2y)^2+8y(x+y)]/4x=[x^2-4y^2-x^2-4y^2+4xy+8xy+8y^2]/4x=12xy/4x=3y

两式相加2x-y+3x+y=7+85x=15x=3y=2x-7=2x3-7=-1如果本题有什么不明白可以追问,

首先求齐次方程通y'-2y=0特征方程：x-2=0x=2为特征根∴y=Ce^(2x)设方程的一个特解为y=Ae^x+ax+b代入方程：Ae^x+a-2Ae^x-2ax-2b=-Ae^x-2ax+a-2

1:x+y=222:2x-y=81+2x+y+(2x-y)=22+8x+2x+y-y=303x=30x=1010+y=22y=12希望能够帮助你!

解13x-2y=9x-3y=2将式2左右两边同时乘以3得3x-9y=6与式1相减有-9y+2y=6-9解得y=3/7代入代2有x-3*3/7=2解得x=23/7故x=23/7y=3/7解2x+y=5x

根号(x+y-8)+根号(8-x-y)=根号(3x-y-4)+根号(x-2y+7),根据二次根式有意义得：X+Y-8≥0,8-X-Y≥0,∴X+Y≥8,X+Y≤8,∴X+Y=8,左边为0,右边两个非负

(x+y)/x=11/88x+8y=11y8x=3yy=8x/3(x-y)/(x+2y)=(x-8x/3)/(x+16x/3)=(-5x/3)/(19x/3)=-5/19

3x=8yx/y=8/3（1）x+y/y=x/y+1=8/3+1=11/3(2)2x+3y/x-2y分子分母同时除以y得=(2x/y+3)/(x/y-2)=(16/3+3)/(8/3-2)=(25/3

X+Y分之X-Y等于3x=-2yX+Y分之2(x-y)减X+Y分之3X+Y=(-x-3y)/(x+y)=1

因为(x-y)/(x+y)=3,则(x＋y)/(x－y)＝1/3则5(x-y)(x+y)-(x+y)/2(x-y)＝5*3-1/(3*2)=15-1/6=89/6

先一个一个的展开括号项,再同项合并就行了啊[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x=[xx-xy-(xy-yy)+x(x-y)+y(x-y)]÷2x=[xx-xy-xy+yy+xx-

x平方+8x+16+y平方+6x+9=0(x+4)平方+(y+3)平方=0∴x+4=0y+3=0∴x=-4,y=-3原式=(x+2y)(x-2y)/(x+2y)平方-x/(x+2y)=(x-2y)/(

你确定答案是-14

解9y=3x-(x-1)2x-9y+1=0①4(x+y)-(2x+4)=8y2x-4y-4=0②②-①得：5y-5=0∴y=1将y=1代入①得：2x-9+1=0∴x=4∴方程的解为：x=4,y=1

x+y/y=11/8说明11y=8（x+y）即8x=3y所以x-y/x+2y=3（x-y）/3(x+2y)=（3x-3y）/(3x+6y)=(3x-8x)/(3x+16x)=-5/19

【(x-y)的3次方-8(x-y)的2次方(x+y)+6y(x-y)的平方】/2(x-y)的平方=(x-y)²[x-y-8(x+y)+6y]/2(x-y)²=1/2（x-y-8x-

很累-3x-2y