Question 71·Medium·Linear Inequalities in One or Two Variables
The graph shows all pairs that satisfy a constraint for a club’s weekly participation goals, where is the number of hours spent on planning and is the number of hours spent on outreach.
Which choice gives an inequality that represents the shaded region on the graph?
For a graphed linear inequality, first determine the boundary line equation using two points on the line (slope and intercept). Then use the shading to decide whether the inequality is “greater than” or “less than,” and use the line style: dashed means strict ( or ) and solid means inclusive ( or ). Finally, rewrite into the form that matches one of the answer choices.
Hints
Use the two labeled points
Find the slope of the boundary line using and .
Write the line equation
Use the point with to identify the -intercept, then write the line in slope-intercept form.
Decide between , , , and
Shading above the line means is greater than the line. A dashed boundary means the line itself is not included (strict inequality).
Desmos Guide
Graph the boundary line
In Desmos, enter y=-1/2 x + 4 and confirm it passes through and .
Test the shaded side
Try a point clearly in the shaded region (for example, ) and check whether it makes x+2y>8 true.
Match the inequality to the shading
Enter x+2y>8 in Desmos and confirm the shaded region matches the graph; the correct inequality is .
Step-by-step Explanation
Find the boundary line equation
The dashed line passes through and . Its slope is
Since the line goes through , the -intercept is , so the boundary line is
Use shading and line type to choose the inequality
The region above the line is shaded, so must be greater than the line’s value.
Because the boundary is dashed, points on the line are not included, so the inequality is strict:
Rewrite in standard form and select the choice
Multiply by to clear the fraction:
Add to both sides:
Therefore, the correct choice is .