SAT Math · Nonlinear equations in one variable · medium

If |2x - 5| = 11 and x is negative, what is the value of x?

If ∣2x−5∣=11|2x - 5| = 11 and xx is negative, what is the value of xx?

Answer and explanation

Answer: -3

An absolute value equation splits into two cases. Case 1: 2x−5=112x - 5 = 11 gives 2x=162x = 16, so x=8x = 8. Case 2: 2x−5=−112x - 5 = -11 gives 2x=−62x = -6, so x=−3x = -3. The problem states that xx is negative, so we keep only x=−3x = -3. Check: ∣2(−3)−5∣=∣−11∣=11|2(-3) - 5| = |-11| = 11. Common wrong answers: 8 is the other valid solution to the equation but it is positive, so it is excluded. Another wrong answer is −8-8, which results from solving the second case incorrectly, and a third is 3, from dropping the sign.

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