Question 202387
-118<-7a+1<1
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subst  1
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-119<-7a<0
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divide  by  -7,,,flip  inequality  signs
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17>a>0
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check
a>17,,test  point  a=20,,,-7(20)+1=-139,,,-118<-139<1,,,,,no
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a<0,,,test  point a=-1,,-7(-1)+1= 8,,,,-118<8<1,,,,,no
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17>a>0,,,test  point,a=10,,-7(10)+1=-69,,,-118<-69<1,,,ok
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therefore confirmed,,17>a>0