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1.k=-2
2.y=(3x+4)/2; y=7/2
3.2-a=3a+4
4a=-2
a=-1/2
4.{x+y=-1
{x-y=3
5.(1,4)(2,3)(3,2)(4,1)共4个
6.-m+2n=10
m+3n=10
5n=20
n=4,m=10-3×4=-2
即m=-2,n=4
7.5x-3=3(y+1)
8.2(m-1)-(m+1)+m-3=0
2m-2-m-1+m-3=0
2m=6
m=3
9.-3x+y-4=0
3-4x-y=0
相加,得
-7x-1=0
x=-1/7
y=3x+4=-3/7+4=25/7
10.12x-3-6+16y
=12x+16y-9
=4(3x+4y)-9
=4×9-9
=36-9
=27
2.y=(3x+4)/2; y=7/2
3.2-a=3a+4
4a=-2
a=-1/2
4.{x+y=-1
{x-y=3
5.(1,4)(2,3)(3,2)(4,1)共4个
6.-m+2n=10
m+3n=10
5n=20
n=4,m=10-3×4=-2
即m=-2,n=4
7.5x-3=3(y+1)
8.2(m-1)-(m+1)+m-3=0
2m-2-m-1+m-3=0
2m=6
m=3
9.-3x+y-4=0
3-4x-y=0
相加,得
-7x-1=0
x=-1/7
y=3x+4=-3/7+4=25/7
10.12x-3-6+16y
=12x+16y-9
=4(3x+4y)-9
=4×9-9
=36-9
=27