Bunuel
Is x^2 – x – 12 = 0?
(1) x^2 + x – 6 = 0
(2) x < 0
Question Stem Analysis:We need to determine whether x^2 - x - 12 = 0. Factoring the left hand side, we obtain (x - 4)(x + 3) = 0, which means the solutions of the quadratic equation are x = 4 and x = -3. Thus, the question becomes "Is x equal to 4 or -3?".
Statement One Alone:\(\Rightarrow\) x^2 + x - 6 = 0
We can factor this expression as (x + 3)(x - 2) = 0, so we can conclude that x = -3 or x = 2. If x = -3, then the answer to the question "Is x equal to 4 or -3?" is yes. If x = 2, then the answer to the same question is no. Statement one alone is not sufficient.
Eliminate answer choices A and D.
Statement Two Alone:\(\Rightarrow\) x < 0
Using this statement, we can eliminate the possibility of x = 4; however, x can still equal -3 or some other negative number. Statement two alone is not sufficient.
Eliminate answer choice B.
Statements One and Two Together:From statement one, we know x is either -3 or 2. From statement two, we know x < 0. Combining these two facts, it follows that x is equal to -3. This answers the question. Statements one and two together are sufficient.
Answer: C