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2x<4?

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2x<4?

by oquiella » Sat Oct 31, 2015 1:22 pm
87. If x is a positive number, is x < 2?
(1) x2+2x-3=0
(2) 2x ≤ 4


I thought statment 2 answers the questions because i got x is less than or equal to 2. Why does statment 2 not work? I do no like the explanation they gave



Statement (1)
x2+2x-3=0
x = -3 or 1
Since it is given that x is a positive number, x = 1
Therefore x < 2; SUFFICIENT
Statement (2)
2x ≤ 4
x ≤ 2
Here x may be equal to or less than 2; NOT SUFFICIENT.
The correct answer is A
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by theCEO » Sat Oct 31, 2015 4:35 pm
oquiella wrote:87. If x is a positive number, is x < 2?
(1) x2+2x-3=0
(2) 2x ≤ 4


I thought statment 2 answers the questions because i got x is less than or equal to 2. Why does statment 2 not work? I do no like the explanation they gave
Is x < 2 can be rephrased as is x ≤ 1.999....?

1) x^2+2x-3=0
x^2 + 3x - 1x - 3 = 0
x(x+3) -1(x+3)= 0
(x+3)(x-1) = 0 ; x=-3 or x=1
Is -3 or 1 less than or equal to 1.999.... -> yes
Therefore statement is sufficent

2) 2x ≤ 4
x ≤ 2 - this means x value is less than or equal to 2
If x = 2, the answer to question is x ≤ 1.999....? No
If x = 1, the answer to question is x ≤ 1.999....? Yes
Because we can have a yes or no statement for this statement, it is insufficent

Ans = a
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