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statement 1: x >0
x can be 2 or 10 , so clearly insufficient

statement 2: \(\sqrt{x^{3}-9x+4}\) > \(2\)
\(x^{3}-9x+4\) > \(4\)
\(x^{3}-9x\) > \(0\)
\(x(x^{2}-9)\) > \(0\)
\(x(x-3)(x+3)\) > \(0\)
so we have two valid intervals: \(x\) > \(3\) and \(0\) > \(x\) > \(-3\) . since one of them is \(> 3\) and the other is \(< 3\), so insufficient

by combining 1 and 2:
knowing \(x\) > \(0\) excludes the interval \(0\) > \(x\) > \(-3\), so left with the other interval \(x\) > \(3\), so sufficient
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Question for managing time: how did you all get -3<x<0 quickly enough? were you able to test values within the time limit or did you surmise from the shape of a cubic graph?
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Question for managing time: how did you all get -3<x<0 quickly enough? were you able to test values within the time limit or did you surmise from the shape of a cubic graph?
Hi sfoo . the answer is "by speed drawing"

follow these steps:
step 1 : find key points of the equation
in our case, the equation is \(x(x-3)(x+3)\) > \(0\)
so the points are 0,3,-3

step 2: draw them on a straight light in ascending order
so you will have : -----------------------(-3)------------(0)----------(3)-------------

step 3: draw a parabolic line "like an "S" (wavy line starting with the biggest number, starting from the positive side (because x has positive sign beside it))

step 4: since the inequality is asking for intervals > 0, so we take the intervals above the straight line.

note: beware of the inequalities whether it is > or >=

try plugging in different equations in this plot to get sense of how things work: https://fooplot.com/#W3sidHlwZSI6MCwiZXEiOiJ4XjIiLCJjb2xvciI6IiMwMDAwMDAifSx7InR5cGUiOjEwMDB9XQ--
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Question for managing time: how did you all get -3<x<0 quickly enough? were you able to test values within the time limit or did you surmise from the shape of a cubic graph?

Check out the below link to learn how to quickly find solutions for such inequalities:

https://gmatclub.com/forum/wavy-line-me ... 24319.html
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Hi,

can someone help me with this question? I think there is some gap in my understanding. From stat1 we got that x>0. From Stat2 we got that x>0 or x>-3 or x>3. But when we combine the two statements we are getting x>0 or x>3. How we can come up with the conclusion that x will be greater than 3.
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Hi,

can someone help me with this question? I think there is some gap in my understanding. From stat1 we got that x>0. From Stat2 we got that x>0 or x>-3 or x>3. But when we combine the two statements we are getting x>0 or x>3. How we can come up with the conclusion that x will be greater than 3.

The ranges you get are not correct. I think you should brush up fundamentals on inequalities. I think the links below should help.

9. Inequalities



For more check Ultimate GMAT Quantitative Megathread



Hope it helps.
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agar123
Hi,

can someone help me with this question? I think there is some gap in my understanding. From stat1 we got that x>0. From Stat2 we got that x>0 or x>-3 or x>3. But when we combine the two statements we are getting x>0 or x>3. How we can come up with the conclusion that x will be greater than 3.

The ranges you get are not correct. I think you should brush up fundamentals on inequalities. I think the links below should help.

9. Inequalities



For more check Ultimate GMAT Quantitative Megathread



Hope it helps.

Thank you for the link. will rebrush my basic first.. :)
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