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range for t

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range for t

by shahdevine » Mon Aug 31, 2009 12:15 pm
Which of the following expresses the range of possible values for t if -6 < |5t - 8| < 1?

a) 2/5<t<14/5
b)2/5<t<9/5
c)7/5<t<14/5
d)7/5<t<9/5
e)9/5<t<14/5

oa after some discussion.

i chose c...why can't it be c. plz explain
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by larrybird » Mon Aug 31, 2009 2:03 pm
Chech when expression within absolute value is positive and negative:

Case 1:
-6<5t-8<1
2<5t<9
2/5<t<9/5

Case 2:
-6<-(5t-8)<1
-6<-5t+8<1
-14<-5t<-7
-14/5<-t<-7/5
Multiply all by -1:
7/5<t<14/5

Finnaly the intersection of both Cases is:
7/5<t<9/5
IMO: D
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