Bunuel
12 Days of Christmas GMAT Competition with Lots of FunWhich of the following can never be correct?
I: \(x < x^2 < 1-x\)
II: \(x < x^2 < \frac{1}{x} \)
III: \(x < \frac{1}{x} < x^2\)
IV: \(x < \frac{1}{x} < x^2 < x^3\)
A. II only
B. II and III only
C. II and IV only
D. I, II, and IV only
E. I, II, III, and IV only
Explanation-
In the question statement, there is no limitations define for choosing the value of x
So, x can be any value ............, 1, 10, 0.4, 0.1, 0.5, 0, -0.1, -0.4, -5, -10, .............
We will check the given conditions by substituting any values for x. If the condition holds true for even one value of x, then that condition can be correct.
In this type of question, if we get even a single value correct for a particular condition, the condition will hold true
I: \(x < x^2 < 1-x\)
Case 1: If x = 1,
1 < 1^2 < 1-1
The condition does not holds true
Case 2: If x= -0.1,
-0.1 < 0.01 < 1.1
The condition holds true
So, even though the condition doesn't hold true for 1 value of x, it holds true for other value of x. Therefore, this condition does not fall under 'can never be correct'
II: \(x < x^2 < \frac{1}{x} \)
Case 1: x= -0.1
-0.1 < 0.01 < -10
The condition does not holds true
Checked for multiple values of x, but the condition does not hold true for any value of x
III: \(x < \frac{1}{x} < x^2\)
Case 1: x= -10
-10 < -0.1 < 100
The condition holds true
IV: \(x < \frac{1}{x} < x^2 < x^3\)
Case 1: x = 0.5
0.5 < 2 < 0.25 < 0.025
The condition does not holds true
Case 2: x = -0.1
-0.1 < -10 < 0.01 < -0.001
The condition does not holds true
Checked for multiple values of x, but the condition does not hold true for any value of x
Correct answer is C