用代入法解下列方程组(1)2x=3-y
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5x-4y=-1--------------①2x+3y=18--------------②解①得:X=(4Y-1)/5把X=(4Y-1)/5代入②得:2*(4Y-1)/5+3Y=182(4Y-1)+
4x-5y=3……①3x-2y=1……②由①得:y=(4x-3)/5……③③代入②得:3x-2×(4x-3)/5=1∴15x-8x+6=5∴7x=﹣1∴x=﹣1/7将x=﹣1/7代入③得:y=﹣5/7
3X+Y=11式X-2Y+1=02式由2式得x=2Y-1代入1式6Y-3+Y=1Y=4/7X=2*4/7-1=1/7很高兴为您解答,【学习宝典】团队为您答题.请点击下面的【选为满意回答】按钮,
(1)x=y-5代入(2)3(y-5)+2y=103y-15+2y=105y=25y=5x=y-5=0
x+2y=3x=3-2yy=-2(3-2y)y=-6+4y3y=6y=2x=-1
x=2y①2x+y=5②①代入②4y+y=5y=1x=2
(1)4x-2y=5——4x=5+2y;——x=(5+2y)/4;代入到(2)(2)3x-4y=153(5+2y)/4-4y=15(通分)3(5+2y)-16y=6010y=-45y=-4.5x=-1
x+y=12…………①2x+y=20…………②②-①得x=8把x=8代入①得8+y=12y=4∴x=8,y=4很高兴为您解答,【the1900】团队为您答题.请点击下面的【选为满意回答】按钮.
2y-x=10①x=3y②②代入①2y-3y=10-y=10y=-10x=-30
y=x+1.(1)2x-3y.(2)将方程(1)代入(2)得到2x-3X-3----->-X-3
x=1/2把x带入(2)式子中3*1/2-y=6y=3/2-6y=-9/2
X-Y=13①X=6Y-7②将②代入①6Y-7-Y=135Y=20Y=4代入②X=6*4-7=17则X=17,Y=4
3x=4y∴x=4y/3代入x-2y=-5得4y/3-2y=-5,即-2y/3=-5∴y=7.5∴x=10
2x+3y=40,x-y=-52x+3y=403x-3y=-155x=25x=55-y=-5y=10x=5y=10
2(x-3)-11=2y2(x-y)=17x-y=17/2x-3/2-3y=0x-y-2y=3/217/2-2y=3/22y=7y=7/2x=12
(1)3x+2(2x-3)=83x+4x-6=87x=14x=2y=4-3y=1(2)y=2x-53x+4y=23x+4(2x-5)=23x+8x-20=211x=22x=2y=4-5y=-1
y=2x-1代入方程2:4x-3(2x-1)=14x-6x+3=1-2x=-2x=1故y=2x-1=1解即为x=1,y=1
y=2xx+2y=3x+2*(2x)+35x=3x=3/5y=2*(3/5)=6/5
2A+B=3①4A-3B=5②由①得B=3-2A③把③代入②得4A-3(3-2A)=5化简,得4A-9+6A=510A=14解得A=7/5把A=7/5代入③,得B=3-2x7/5解得B=5/1
y=x+2代入2x-y=-12x-x-2=-1x=1,y=x+2=32x-3y=-54x+3y=-1x=(3y-5)/2代入4x+3y=-16y-10+3Y=-19Y=9Y=1X=(3y-5)/2=-