解方程组2x-y-2=0和x-y 3=0-搜答案-拍题作业网

分别把x=1y=-1和x=2y=2代人二元一次方程ax+by+4=0中得a-b+4=02a+2b+4=0解得：a=-3b=1所以二元一次方程ax+by+4=0为-3x+y+4=0当x=3y=4时-3x

由题意知因为x+y-a=0,x-2y=5所以解得X=（5+2a）/3,Y=（a-5）/3又因为x＞1,y≤1所以-1

7x+3y=69(1)2x-y=16(2)(1)+3*(2)得13x=69+4813x=117x=9y=2x-16=18-16=2x=9y=2a

X/2+Y/3=13X/3-Y/4=33X+2Y=13*64X-3Y=3*123X+2Y=784X-3Y=36X=(36+3Y)/4代入1式108+9Y+8Y=31217Y=204Y=12X=18

楼主自己把第二个代入第一个慢慢算吧,默默飘走.

(x+y)(x-y)-(x+y)=0(x+y)(x-y-1)=0若x-y-1=0y=x-1则4x^2-x^2+2x-1+2x-x+1=03x^2-3x=03x(x-1)=0x=0,x=1y=x-1若x

X^2-y^2-x-y=0.(1)4x^2-y^2+2y-1=0.(2)根据（1）:(x+y)(x-y)-(x+y)=0(x+y)(x-y-1)=0x+y=0.(3)或x-y-1=0.(4)根据（2）

2x+y=2m-1①x+2y=m②①+②得3x+3y=3m-1x+y=m-1/3①-②得x-y=m-1∵x+y>0,x-y0,m-11/3,m

你看一下我做的有点急不知道对不

x等于二分之一,y等于三分之一

一式乘以3,减去,二式乘以2,消去x,你就会了

x:y=2:3和5x+3y=38y=3x/2;5x+3y=385x+9x/2=3819x=76x=4y=63y+x/y=8和9y-2x/y=96y+2x/y=16;9y-2x/y=915y=25y=5

2x+y=1-m,x+2y=2,则3x+3y=3-m>0,则m

（1）7x+3y=23①2x-y=9②②×3得：6x-3y=27③③+①得：13x=50x=50/13代入②得：2×50/13-y=9-y=9-100/13-y=17/13y=-17/13∴x=50/

6/x-7/y=402/x-5/y=86/x-7/y=406/x-15/y=24x=1/9y=1/2

解题过程如下..已知2x-y=73x+y=8则2x-y+3x+y=7+8=15即5x=15x=3将x=3代入2x-y=7即6-y=7得y=-1

∵3X-5Y=-2.(1)2X+7Y=40.(2)∴由(2)*3-(1)*2,得31Y=124,即Y=4把Y=4代入(1),得X=6故原方程组的解是：X=6,Y=4

|x+3y|+|5x-y+2|=52x+y=1由②得：y=1-2x...代入得|x+3-6x|+|5x-1+2x+2|=5|3-5x|+|7x+1|=53-5x+7x+1=52x+4=5x=1/2.①

展开x^2-2y^2-xy=-5x^2-2y^2+xy=7所以x^2-2y^2=1xy=6上式除以下式,解分式方程x/y=3/2或-4/3(舍去)所以x^2=9y^2=4x=3y=2或x=-3y=-2

(x+y)/2+(x-y)/6=1x/2+x/6+y/2-y/6=12x/3+y/3=12x+y=3(1)3(x+y)-4(x-y)=43x+3y-4x+4y=4-x+7y=4(2)(1)+2*(2)