怎么用加减消元法解6x-5y=3.6x y=-15
来源:学生作业帮助网 编辑:作业帮 时间:2024/05/16 18:30:46
1,x+y/2+x-y/3=6即:5x-y=36①4(x+y)-5(x-y)=2即:-x+9y=2②①+②*5==可接2,先化整:3(x+y)+2(x-y)=36①4(x+y)-5(x-y)=2②①*
将2x-y=4扩大两倍:4x-2y=8①4x+3y=6②②-①:5y=-2y=-2/5x=9/5
5x-3y=2(1)4y+2x=6(2)(1)×2-(2)×5,得-6y-20y=4-30即-26y=-26解得y=1把y=1代入(1)得5x-3=2即5x=5解得x=1∴x=1,y=1
(x+y)/2+(x-y)/3=6……①4(x+y)-3(x-y)=0……②由①:3(x+y)+2(x-y)=363x+3y+2x-2y=365x+y=36……③由②:4x+4y-3x+3y=0x+7
3x+4y=14——①5x-6y=36——②∴①*5-②*3得:38y=-38解得:y=-1代入①式得:x=6∴x=6y=-1
X+Y=7①3x+5y=17②①×3得3X+3Y=21③②-③得2y=-4y=-2把y=-2代入①得x=9所以原方程组的解的x=9y=-2X+Y=7①3x+5y=17②由①得y=7-x③把③代入②得3
3x-5y=7;4x+2y=56x-10y=1420x+10y=25两式相加26x=39x=1.55y=3x-75y=4.5-75y=-2.5y=-0.5
3(x-1)=y+52(y+1)=x+13x-3=y+52y+2=x+13x-y=8x-2y=16x-2y=16①x-2y=1②①-②得5x=15所以x=3把x=3代入②得3-2y=1所以y=1所以方
x+y=412x-y=521式+2式得3x=9解得x=3y=1
4x+3y=3①3x+5y=-6②3①-4②得:-11y=3×3+6×4=33y=-3x=(3-3y)/4=32x+5y=5,①3x-5y=10②①+②得:5x=15,x=3y=(5-2x)/5-1/
第二个方程,展开先得到.5x-3y=11,第一个方程x-y=3.变成,5x-5y=15.,两式相减.5x-5y-(5x-3y)=15-11.得到y=-2.所以,x=1
整理方程①3﹙x+y﹚=36-2﹙x-y﹚3x+3y=36-2x+2y3x+3y+2x-2y=365x+y=36③整理方程②4x+4y-5x+5y=2-x+9y=2x=9y-2④④代入③,得5﹙9y-
x-y+3=0(1)7x+5y=9(2)(1)*5+(2)得:12x+15=9x=-1/2代入(1)得:y=-1/2+3=5/2所以,方程组的解是:x=-1/2;y=5/2
①[(x+y)/2]+[(x-y)/3]=5②[(x+y)/2]+[(x-y)/3]=-1①-②(x-y)/3=6x-y=18,x+y=2相加2x=20,x=10,则y=-8
3x+2y=5(1)2x-3y=8(2)(1)式等式两边同乘以1.5得4.5x+3y=7.5(3)(3)+(2)得6.5x=15.5解得x=31/13代入原方程解得y=-14/13
把两方程左边跟左边相加右边跟右边相加得6x-4y+(3x+4y)=37+(-5)9x=32x=32/9
式一+式二,消去y,得9x=33则x=11/3,代回式一有y=15/4
4x-5y=5①,2x+3y=-25②②2=4x+6y=-50③③-①=11y=-55y=-5代入①解得x=-5
3x+5(x+y)=36即8x+5y=36.(1)3y+4(x+y)=36即4x+7y=36.(2)(1)-(2)*2得-9y=-36y=4代入(2)得4x+28=364x=8x=2解得x=2y=4
x-y=4(1)2x+y=5(2)(1)+(2)得:3x=9解得:x=3把x=3代入(1)得:3-y=4解得:y=-1所以方程组的解为:x=3y=-1