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Re: If b is positive, is ab positive? [#permalink]

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11 Aug 2017, 05:42

If b is positive, is ab positive? 1. \(a^2b>0\)

Since we are given b is positive, if a is either positive or negative, the expression \(a^2b>0\) holds true. Case 1: a=-3, b=2 Here, ab is negative Case 2: a=3, b=2 Here, ab is positive(Insufficient) 2. \(a^2+b=13\)

Since we are given b is positive, if a is either positive or negative, the expression \(a^2+b=13\) holds true. Case 1: a=-3, b=5 Here, ab is negative Case 2: a=3, b=5 Here, ab is positive(Insufficient)

Even combining both the statements, we will be left with two options in the first one - both a and b are positive in the second one - a is negative and b is positive. (Insufficient)(Option E) _________________

Re: If b is positive, is ab positive? [#permalink]

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11 Aug 2017, 08:32

given b>0 1) (a^2).b>0 from this b>0 then a can be positive as well as negative, so sign of axb can't be determined. A,D ruled out 2) (a^2)+b=13 , b>0 and b <13 a can have Positive and Negative values, also if b>13 , then a is not defined hence sign of axb can't be determined. B ruled out.

Combining both , a^2+b = 13 and (a^2) x b > 0 cant solve the problem with the sign from above 2 statements, a can be negative as well as positive since its square will always be positive and therefore C ruled out

Answer is E _________________

Give Kudos for correct answer and/or if you like the solution.

Re: If b is positive, is ab positive? [#permalink]

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11 Aug 2017, 11:52

St:1 says nothing but what is given in question. B is positive. A can be -ve as well as +ve.Insufficient St:2 says that a2 will be positive .Again A can be -ve as well as +ve.Insufficient