Last Updated on May 10, 2023
GMAT OFFICIAL GUIDE DS
Solution:
We are given that x is an integer, and we must determine whether x|x| < 2^x.
Statement One Alone:
x< 0
Since we are given that x is less than 0, we can substitute negative integers for x into the inequality x|x| < 2^x.
x = -1
Is -1|-1| < 2^-1 ?
Is -1 * 1 < 2^-1 ?
Is -1 <½ ?
Yes!
Without substituting any other negative integers for x, we see that x|x| will always be negative when x is less than zero, and 2^x will always remain positive, because the base 2 is positive and a positive base raised to any power is always positive. Statement one alone is sufficient to answer the question. We can eliminate answer choices B, C, and E.
Statement Two Alone:
x = -10
Using the same logic that we used in statement one, we see that when x = -10, x|x| is less than 2^x. Statement two alone is sufficient to answer the question.
Answer: D
