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.

  1. 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 \(b = -3\).

  2. 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.

  3. 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.

  4. 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:

\[ \{(x,y)\in\mathbb{R}^2 : y < x – 3\} \]

See full solution

Graph

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Algebra FAQs

What line is the boundary for the inequality \(y < x - 3\)?.

The boundary is the line given by the equality \(y = x - 3\). Graph that line first; then use the inequality to decide which side to shade.

Should the boundary line be dashed or solid?

Use a dashed line because the inequality is strict (\(<\)), so points on the boundary \(y = x - 3\) are not included.

How do I find the slope and y-intercept?

In \(y = x - 3\), the slope is \(1\) and the \(y\)-intercept is \((0,-3)\). From \((0,-3)\) move up \(1\) and right \(1\) to plot the line..

Which side of the line do I shade?

Pick a test point not on the line, like \( (0,0) \). Since \(0 < 0 - 3\) is false, shade the side that does not contain \( (0,0) \); that is, shade the region below the line.

What are the intercepts of the boundary line?.

y-intercept: \( (0,-3) \). x-intercept: set \(y=0\), so \(0 = x - 3\) gives \(x=3\); x-intercept is \( (3,0) \).

How can I rewrite the inequality in a different form?

How can I rewrite the inequality in a different form?

How do I test whether a specific point \( (a,b) \) satisfies the inequality? .

Substitute into \(y < x - 3\): check if \(b < a - 3\). If true, the point is in the shaded region; if false, it is outside (and if equality holds, it's on the boundary but not included here)..

How would the graph change for \(y \le x - 3\)?.

For \(y \le x - 3\) use a solid boundary line (points on the line included) and shade the same side (below the line), since the inequality direction is unchanged.

How to graph this using slope-intercept steps?

Plot the y-intercept \(-(0,-3)\). From there use slope \(1\): for each step, go right \(1\) and up \(1\) to get additional points, draw a dashed line through them, then shade below.
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