Question bank / Linear inequalities in one or two variables

Math · AlgebraMedium

For which of the following inequalities are both (0,0)(0, 0) and (3,−1)(3, -1) solutions?

A

y>x−2y > x - 2

B

y<−x+1y < -x + 1

C

y≥−xy \ge -x

D

y≤2x−1y \le 2x - 1

Show answer and explanation

Answer: C

Test both points in each inequality. For y≥−xy \ge -x: at (0,0)(0, 0), 0≥00 \ge 0 is true, and at (3,−1)(3, -1), −1≥−3-1 \ge -3 is true. So both points are solutions of choice C. Each of the other inequalities fails for at least one of the points.

Choice A works for (0,0)(0, 0) but fails for (3,−1)(3, -1), since −1>1-1 > 1 is false.

Why the other choices are wrong

  • A. (0, 0) works, but at (3, -1) it says -1 > 1, which is false.
  • B. (0, 0) works, but at (3, -1) it says -1 < -2, which is false.
  • D. At (0, 0) it says 0 ≤ -1, which is false.
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