y-x=1 10x+y> 10x+y30 10x+y

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y-x=110x+y>10x+y3010x+yy-x=110x+y>10x+y3010x+yy-x=110x+y>10x+y3010x+yy-x=1,y=x+1代入10x+(x+1)>30,10x+x

y-x=1 10x+y> 10x+y30 10x+y
y-x=1 10x+y> 10x+y30 10x+y

y-x=1 10x+y> 10x+y30 10x+y
y-x=1,y=x+1
代入
10x+(x+1)>30,10x+x+1>30,11x>29,x>29/11
y=x+1>(29/11)+1>40/11
10x+(x+1)

① 先把y-x=1变形成y=1+x
② 把y=1+x带入10x+y>30,10x+y<42
得10x+1+x>30
x>29/11
10x+1+x<42
x<41/11
∴29/11<x<41/11
③ 再把y-x=1变形成x=y-1
④ 把...

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① 先把y-x=1变形成y=1+x
② 把y=1+x带入10x+y>30,10x+y<42
得10x+1+x>30
x>29/11
10x+1+x<42
x<41/11
∴29/11<x<41/11
③ 再把y-x=1变形成x=y-1
④ 把x=y-1带入10x+y>30,10x+y<42
得10(y-1)+y>30
y>40/11
10(y-1)+y<42
y<52/11
∴40/11<y<52/11

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