Question 59·Medium·Linear Inequalities in One or Two Variables
Consider the system of inequalities
For which of the following tables are all the ordered pairs listed solutions to the system?
For systems-of-inequalities questions with small tables of candidate points, the fastest SAT approach is usually direct substitution: for each option, test just one ordered pair by plugging its and into both inequalities; if either inequality fails, eliminate that entire option. Continue until only one table remains, then quickly verify that all three ordered pairs in that table satisfy both inequalities to confirm your answer without needing to graph.
Hints
Focus on what a solution to a system means
For an ordered pair to be a solution to the system, what must happen when you plug and into both inequalities?
Use substitution instead of graphing
Pick one ordered pair from a table and substitute its and into and into . If it fails either inequality, that whole table cannot be the answer.
Eliminate options efficiently
You do not need to check every pair in every table. Once you find one ordered pair in a table that does not satisfy the system, you can cross out that entire option.
Verify all pairs in your final choice
Once you think you’ve found the correct table, make sure you have checked that each of its three ordered pairs makes both inequalities true.
Desmos Guide
Graph the inequalities
In Desmos, enter the inequalities in -form:
- Type
y <= (3x - 6)/2for . - Type
y < 5 - xfor . You should see two shaded regions; the solution set to the system is where the shading overlaps.
Plot the points from each table
For each answer choice, enter its three ordered pairs as points, for example (4,2), (3,0), (2,2) for one table. Desmos will plot these points on the same coordinate plane as the shaded solution region.
Check which table’s points lie in the overlap
For each table, see whether all three of its points lie inside the overlapping shaded region of the two inequalities (not just on one region or outside both). The correct answer is the table whose three points all lie in this overlapping region.
Step-by-step Explanation
Understand what it means to be a solution to the system
The system is
An ordered pair is a solution only if both inequalities are true when you plug in and . If even one inequality is false, the pair is not a solution, and a table is correct only if all its pairs are solutions.
Test the ordered pairs in option A
Option A lists , , and .
Check :
- First inequality: , and is true.
- Second inequality: , and is false.
Because does not satisfy , it is not a solution to the system. Therefore, option A cannot be correct, since not all of its ordered pairs are solutions.
Test the ordered pairs in options B and C
Option B lists , , and .
Check :
- First inequality: , and is false.
So fails the first inequality, meaning option B cannot be correct.
Option C lists , , and .
Check :
- First inequality: , so is true.
- Second inequality: , and is false.
So fails the second inequality, meaning option C cannot be correct either.
Verify the remaining option and conclude
The remaining table lists , , and .
Check :
- First inequality: , and is true.
- Second inequality: , and is true.
Check :
- First inequality: , and is true.
- Second inequality: , and is true.
Check :
- First inequality: , and is true.
- Second inequality: , and is true.
All three ordered pairs satisfy both inequalities, so the correct table is the one with , , and (option D).