- 帮帮我,谢谢了(1)2x
- (1)2x-y=5
7x-3y=20
(2)4x-y=1
y=2x+3
(3)5x+y=2
x-3y=4
(4)3x-2y=1
2x+3y=-7
请解答二元一次方程,谢谢了,要过程,答案详细些
- 2x-y=5……⑴
7x-3y=20……⑵
⑵-⑴*3:x=5,代入⑴,得到:y=5
(2)4x-y=1……⑴
y=2x+3……⑵
⑵代入⑴:2x=4 ==> x=2,代入⑵:y=7
(3)5x+y=2……⑴
x-3y=4……⑵
⑴*3+⑵:16x=10 ==> x=5/8,代入⑴:25/8+y=2 ==> y=-9/8
(4)3x-2y=1……⑴
2x+3y=-7……⑵
⑴*3+⑵*2:x=-11/13,代入⑴:-33/13-2y=1 ==> y=-23/13