Math Problem Statement

Mr. Aguilar placed a graphed system of linear inequalities on the board.  

 

Which system of linear inequalities is best represented by the graph?

A.

y ≤ 3x − 9y ≤ 3x − 9

y ≥ −45x + 7y ≥ −45x + 7

B.

y ≥ 3x − 9y ≥ 3x − 9

y ≥ −45x + 7y ≥ −45x + 7

C.

y ≥ 3x − 9y ≥ 3x − 9

y ≤ −45x + 7y ≤ −45x + 7

D.

y ≤ 3x − 9y ≤ 3x − 9

y ≤ −45x + 7y ≤ −45x + 7

Solution

To determine which system of linear inequalities matches the graph, let's analyze the inequalities provided in each option. Here’s a breakdown of what you need to look for:

Key elements to check:

  1. Inequality Direction:

    • yy \leq or yy \geq indicates if the solution region lies below or above the line.
    • yy \leq means shading below the line (or on the line if equality holds).
    • yy \geq means shading above the line (or on the line if equality holds).
  2. Slope and Y-Intercept:

    • The inequalities are in the form ymx+by \leq mx + b or ymx+by \geq mx + b, where mm is the slope and bb is the y-intercept.

    • For the line y=3x9y = 3x - 9:

      • Slope m=3m = 3
      • Y-intercept b=9b = -9
    • For the line y=45x+7y = -45x + 7:

      • Slope m=45m = -45
      • Y-intercept b=7b = 7

Now, let's interpret each option:

  • Option A:

    • y3x9y \leq 3x - 9 (shading below this line)
    • y45x+7y \geq -45x + 7 (shading above this line)
  • Option B:

    • y3x9y \geq 3x - 9 (shading above this line)
    • y45x+7y \geq -45x + 7 (shading above this line)
  • Option C:

    • y3x9y \geq 3x - 9 (shading above this line)
    • y45x+7y \leq -45x + 7 (shading below this line)
  • Option D:

    • y3x9y \leq 3x - 9 (shading below this line)
    • y45x+7y \leq -45x + 7 (shading below this line)

Choosing the correct system:

The correct system will have:

  • One inequality with yy \leq and one with yy \geq if the solution region is bounded between the two lines.

Thus, Option A is the most likely answer:

  • y3x9y \leq 3x - 9 (shading below)
  • y45x+7y \geq -45x + 7 (shading above)

This option suggests the solution region is between the two lines, matching a typical intersection of two linear inequalities.


Would you like a detailed graph explanation or further clarification?
Here are five related questions to expand your understanding:

  1. How do we determine if an inequality includes the boundary line?
  2. What happens when the slopes of two lines are equal in a system of inequalities?
  3. How do you graph a system of linear inequalities step by step?
  4. How can you tell if a point lies in the solution region of a system of inequalities?
  5. What does it mean if two inequalities have no overlapping solution region?

Tip: When graphing inequalities, use test points (like the origin) to confirm which side of the line should be shaded.

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Math Problem Analysis

Mathematical Concepts

Algebra
Linear Inequalities
Graphing Inequalities
Systems of Inequalities

Formulas

y ≤ mx + b
y ≥ mx + b

Theorems

Solution region theorem for inequalities
Intersection of solution regions for systems of inequalities

Suitable Grade Level

Grades 9-10