初二上学期方程题 4x+y=5 5x+4y=63x-2y=1 2x+3y=13x-2y=7 7x+5y=32x+3y=17 2x-y=-4x+5y=6 2x+y=23x-6y=4 3x+2y=52x+y=73x-4y=53x+y=1x-2y=-1x+y=42x+3y=92x-3y=74x+5y=3x+y=20004x+6y=90003x+5y=113x-2y=42x+3y=215x-2y=5x+y=54x+3y=182x+3y=16x+4y=132x+3y=40x-y=-5

问题描述:

初二上学期方程题
4x+y=5 5x+4y=6
3x-2y=1 2x+3y=1
3x-2y=7 7x+5y=3
2x+3y=17 2x-y=-4
x+5y=6 2x+y=2
3x-6y=4 3x+2y=5
2x+y=7
3x-4y=5
3x+y=1
x-2y=-1
x+y=4
2x+3y=9
2x-3y=7
4x+5y=3
x+y=2000
4x+6y=9000
3x+5y=11
3x-2y=4
2x+3y=21
5x-2y=5
x+y=5
4x+3y=18
2x+3y=16
x+4y=13
2x+3y=40
x-y=-5

4x+y=5 -----(1)
3x-2y=1------(2)
(1)*2+(2):11X=11
解得X=1
把X=1带入(1)得Y=1
即  X=1,Y=1
步骤照这个写
5x+4y=6
2x+3y=1    X=2    Y=-1
3x-2y=7                 7x+5y=3
2x+3y=17 X=55/13 Y=37/13    2x-y=-4  X= -1  Y=2
x+5y=6             2x+y=2
3x-6y=4 X=8/3  Y= 2/3 3x+2y=5  X=-1   Y=4
2x+y=7
3x-4y=5   X=3   Y=1
3x+y=1
x-2y=-1  X=1/7  Y=4/7
x+y=4
2x+3y=9   X=3  Y=1
2x-3y=7
4x+5y=3   X=2   Y=-1
x+y=2000
4x+6y=9000   X=1500  Y=500
3x+5y=11
3x-2y=4   X=2   Y=1
2x+3y=21
5x-2y=5  X= 3 Y=5
x+y=5
4x+3y=18  X= 3 Y=2
2x+3y=16
x+4y=13  X= 5  Y=2
2x+3y=40
x-y=-5  X=5  Y=10

4x+y=5(1)
3x-2y=1(2)
(1)乘以2得:8x+2y=10 (3)
(3)+(2)得:11x=11,所以x=1,
把x=1带入(1)得:
4+y=5,y=5-4,y=1
故x=1,y= 1
3x-2y=7 (1)
2x+3y=17 (2)
(1)乘以3得:9x-6y=21 (3),
(2)乘以2得:4x+6y=34 (4),
(3)+(4) 得: 13x=55,x=11/3,
把x=11/3带入(1)得:y=2
故x=11/3,y= 2
x+5y=6 (1)
3x-6y=4(2)
(1)乘以3后得:3x+15y=18 (3),
(3)-(2)得:21y=14,y=2/3,
把y=2/3带入(2)得:x=8/3
故x=8/3,y= 2/3
2x+y=7(1)
3x-4y=5(2)
(1)乘以4后得:8x+4y=28(3),
(3)+(2)得:11x=33,x=3,
把x=3带入(1)得:
6+y=7,y=7-6,y=1
故x=3,y= 1
3x+y=1(1)
x-2y=-1(2)
(1)乘以2后得:6x+2y=2 (3),
(3)+(2)得:7x=1,x=1/7,
把x=1/7带入(2)得:y=4/7
故x=1/7,y= 4/7
x+y=4 (1)
2x+3y=9 (2)
(1)乘以2后得:2x+2y=8 (3),
(2)-(3)得:y=1,
把y=1带入(1)得:
x+1=4,x=4-1,x=3
故x=3,y= 1
2x-3y=7 (1)
4x+5y=3 (2)
(1)乘以2后得:4x-6y=14 (3),
(2)-(3)得:11y= - 11,y= - 1,
把y= - 1带入(1)得:
2x+3=7,2x=7-3,2x=4,x=2
故x=2,y= —1
x+y=2000(1)
4x+6y=9000(2)
(1)乘以4后得:4x+4y=8000 (3),
(2)-(3)得:2y=1000,y=500,
把y=500带入(1)得:x=1500
故x=1500,y = 500
3x+5y=11(1)
3x-2y=4(2)
(1)-(2)得:7y=7,所以y=1
把y=1带入(1)得:
3x+5=11,3x=11-5,3x=6,x=2
故x=2,y= 1
2x+3y=21(1)
5x-2y=5(2)
(1)乘以2后得:4x+6y=42 (3),
(2)乘以3得:15x-6y=15 (4),
(3)+(4)得:19x=57,x=3,
把x=3带入(1)得:
6+3y=21,3y=21-6,3y=15,y=5
故x=3,y= 5
x+y=5(1)
4x+3y=18(2)
(1)乘以3得:3x+3y=15 (3),
(2)-(3)得:x=3,
把x=3带入(1)得:
3+y=5,y=5-3,y=2
故x=3,y = 2
2x+3y=16(1)
x+4y=13(2)
(2)乘以2得:2x+8y=26 (3),
(3)-(1)得:5y=10,y=2,
把y=2带入(1)得:
2x+6=16,2x=16-6,2x=10,x=5
故x=5,y= 2
2x+3y=40(1)
x-y=-5(2)
(2)乘以2得:2x-2y= - 10 (3),
(1)-(2)得:5y=50,y=10,
把y=10带入(1)得:
2x+30=40,2x=40-30,2x=10,x=5
故x=5,y= 10
5x+4y=6(1)
2x+3y=1 (2)
(1)乘以2得:10x+8y=12 (3);
(2)乘以5得:10x+15y=5 (4),
(4) — (3) 得:7y= —7
所以y = —1,把y = —1带入(2)得:
2x—3=1,2x=4,x=2
故x=2,y= —1
7x+5y=3 (1)
2x-y=-4 (2)
(2)乘以5得:10x-5y=-20(3)
(1)+(3)得:17x= - 17,x= - 1
把x= - 1带入(1)得 :
-7+5y=3,5y=3+7,5y=10,y=2
故x= - 1,y= 2
2x+y=2(1)
3x+2y=5(2)
(1)乘以2得:4x+2y=4 (3)
(3)-(1)得:x=4-5,x=-1
把x=-1带入(1)得:
-2+y=2,y=4
故x= - 1,y= 4