Q. Graph the inequality. \(y < x – 3\)
Answer
Graphing the inequality
The inequality is:
\(y<x-3\)
The boundary line is:
\(y=x-3\)
The line should be dashed because the inequality is strict. A strict inequality uses \(<\), so points on the line are not included in the solution.
Now find key points on the boundary line.
Set \(x=0\).
\(y=0-3=-3\)
So the \(y\)-intercept is \((0,-3)\).
Set \(y=0\).
\(0=x-3\)
\(x=3\)
So the \(x\)-intercept is \((3,0)\).
The slope of the line \(y=x-3\) is \(1\).
Now test the point \((0,0)\).
\(0<0-3\)
\(0<-3\)
This statement is false, so the side containing the origin should not be shaded.
Final result: draw the dashed line \(y=x-3\) and shade the region below the line. The shaded region represents all points that satisfy \(y<x-3\).
Detailed Explanation
We will graph the inequality \(y < x – 3\) with a clear, step-by-step procedure.
- Identify the boundary line.The boundary comes from replacing the inequality sign with equality. The boundary equation is\[ y = x – 3 \]
This is in slope-intercept form \(y = mx + b\) with slope \(m = 1\) and y-intercept \(b = -3\).
- Find two points on the boundary so you can draw the line.Find the y-intercept by setting \(x = 0\):\[ y = 0 – 3 = -3 \]
So one point is \((0,-3)\).
Find the x-intercept by setting \(y = 0\):
\[ 0 = x – 3 \]
\[ x = 3 \]
So another point is \((3,0)\).
Draw the straight line through \((0,-3)\) and \((3,0)\). Because the original inequality is strict (<), draw this boundary as a dashed line to indicate points on the line are not included.
- Decide which side of the boundary to shade.Pick a test point not on the line. A convenient choice is the origin \((0,0)\). Substitute it into the inequality:\[ 0 < 0 – 3 \]
\[ 0 < -3 \]
This is false, so the region containing \((0,0)\) is not part of the solution set. Therefore, shade the opposite side of the dashed line.
For further confirmation, pick a point below the line, for example \((0,-4)\), and test it:
\[ -4 < 0 – 3 \]
\[ -4 < -3 \]
This is true, so points below the line are included in the solution set.
- Conclusion — how the final graph looks.Graph the dashed line through \((0,-3)\) and \((3,0)\). Shade the half-plane that lies below this line (the side that does not contain the origin). The shaded region together with the dashed boundary visually represents all points \((x,y)\) satisfying\[ y < x – 3. \]
Optional set notation for the solution:
\[ \{(x,y)\in\mathbb{R}^2 : y < x – 3\} \]
Graph
Algebra FAQs
What line is the boundary for the inequality \(y < x - 3\)?.
Should the boundary line be dashed or solid?
How do I find the slope and y-intercept?
Which side of the line do I shade?
What are the intercepts of the boundary line?.
How can I rewrite the inequality in a different form?
How do I test whether a specific point \( (a,b) \) satisfies the inequality? .
How would the graph change for \(y \le x - 3\)?.
How to graph this using slope-intercept steps?
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