消元法!!!!!!

Your Question:

2x+y=11...(1)
2x-2y=-4...(2)

(1):

2x+y=11

y=11-2x......(3)

Sub (1) into (2):

2x-2y=-4

2x-2(11-2x)=-4 (∵y=11-2x)

2x-2*11+2*2x=-4

2x-22+4x=-4

2x+4x=4+22

6x=26

x=26/6

x=13/3......(4)

Sub (4) into (3)

y=11-2x

y=11-2*13/3

y=11-26/3

y=33/3-26/3

y=7/3

2007-01-17 23:33:28 補充：
Oh my god, this step is wrong --- 2x＋4x=4＋22It must be:2x＋4x=-4＋226x=18x=18/6x=3......(4)Sub (4) into (3)y=11-2xy=11-2*3y=11-6y=5