Question

1是{y=2x ,x+y=12 2是{x=y-5除以2,4x+3y=65 3是{x+y=11,x-y=7 4是{3x-2y=9,x+2y=3 5是{x-3y=2,y=x

6是{x+y=5,2x+y=8
7是{4x+3y=5,x-2y=4
8是{m-n除以2=2,2m+3n=12
9是{x+3[x+y]=5,x+y=2
10是{3x=2减5y除以2,6x-y=14

Answer 1

1. 将1式代入2，得x+2x=12 3x=12 x=4 代入1得 y=8
2.将1式代入2，得2y-20+3y=65 5y=85 y=17 代入1得 x=3.5
3.由1得y=11-x 代入2，得x-(11-x)=7 2x=18 x=9 y=2
4. 由2得 x=3-2y 代入1，得9-6y-2y=9 8y=0 y=0 x=3