Question 83·Medium·Linear Inequalities in One or Two Variables
Which ordered pair is a solution to the system of inequalities below?
For "Which ordered pair is a solution to the system of inequalities?" questions, it is usually fastest to plug in each answer choice rather than graphing. Treat each pair as , substitute into the first inequality to eliminate any options that fail immediately, then test the remaining ones in the second inequality. Always pay close attention to the inequality symbols (, , , ), especially strict versus non-strict inequalities, and remember that a solution must satisfy all inequalities in the system, not just one.
Hints
Use the definition of a solution to a system
A solution to a system of inequalities must satisfy every inequality in the system at the same time. Think about how you can test that for each ordered pair.
Match the coordinates correctly
Remember that in an ordered pair , the first number is and the second number is . When you substitute, replace with the first number and with the second.
Check one inequality at a time
Start with the first inequality and plug in each answer choice. Eliminate any option that does not make this inequality true, then check the remaining options in the second inequality .
Pay attention to the inequality symbols
Be careful with versus : allows "less than or equal to," but requires the left side to be strictly greater than the right side, not equal or less.
Desmos Guide
Graph the boundary lines of the inequalities
In Desmos, enter the two boundary lines:
y = 3x - 7(this comes from rewriting as )y = -2x + 1(from the second inequality).
Shade the inequality regions
Replace the equations with the inequalities:
- Type
y >= 3x - 7for . - Type
y > -2x + 1for .
Desmos will shade the regions that satisfy each inequality; the solution set to the system is where the shaded regions overlap.
Plot and test each answer choice
Plot each option as a point by typing them into Desmos, for example (−1, −2), (3, 0), etc. Look to see which point lies inside the overlapping shaded region (not just on one region). The point that lies in that intersection region is the solution to the system.
Step-by-step Explanation
Understand what a solution to a system means
A solution to the system must make both inequalities true at the same time:
Each answer choice is an ordered pair , where the first number is and the second number is . You need to plug in each pair and check both inequalities.
Check the first inequality for each option
Use .
Compute for each pair:
- A) : , and (works)
- B) : , and is false (fails)
- C) : , and (works)
- D) : , and (works)
So option B is not a solution because it fails the first inequality. A, C, and D still might work.
Check the second inequality for the remaining options
Now use for the options that passed the first check (A, C, and D):
- A) : right side is . Check if (this is false).
- C) : right side is . Check if (this is true).
- D) : right side is . Check if (this is false).
Only one of these ordered pairs makes both inequalities true.
State the ordered pair that satisfies both inequalities
From the checks:
- Option A fails the second inequality.
- Option B fails the first inequality.
- Option D fails the second inequality.
The only ordered pair that satisfies both and is .