Q. Which graph represents the function \(f(x) = |x + 3|\)?
Answer
The graph is the V-shaped absolute-value graph shifted left 3 units: vertex at (-3,0), opens upward. In piecewise form:
\[
f(x)=\begin{cases}
-(x+3), & x< -3,\\[4pt]
x+3, & x\ge -3.
\end{cases}
\]
Slopes: left arm -1, right arm 1.
Detailed Explanation
Solution — step-by-step
- Recall the definition of absolute value.For any expression u,
\[ |u| = \begin{cases}
u & \text{if } u \ge 0,\\[4pt]
-u & \text{if } u < 0.
\end{cases} \]We will apply this with u = x + 3.
- Write f as a piecewise linear function.Substitute u = x + 3 into the definition:
\[ f(x)=|x+3| = \begin{cases}
x+3 & \text{if } x+3 \ge 0 \;\text{(i.e. } x \ge -3\text{)},\\[4pt]
-(x+3) & \text{if } x+3 < 0 \;\text{(i.e. } x < -3\text{)}.
\end{cases} \]
Simplifying the second branch gives
\[ f(x)=\begin{cases}
x+3 & \text{if } x \ge -3,\\[4pt]
-x-3 & \text{if } x < -3.
\end{cases} \]So the graph is made of two straight-line pieces meeting at x = -3.
- Find the vertex (the corner point).The corner occurs where the inside of the absolute value is zero: x+3 = 0, so x = -3. Evaluate f there:
\[ f(-3) = |{-3}+3| = 0. \]
Thus the vertex is at the point (-3, 0). - Determine slopes and directions of the two arms.For x \ge -3 the formula is f(x) = x + 3, which is a line of slope 1. For x < -3 the formula is f(x) = -x – 3, which is a line of slope -1.
Therefore the graph is a V-shape with the right arm rising with slope 1 and the left arm rising to the left with slope -1. - Check a few points to fix placement.Evaluate f at some sample x-values:
\[ f(0)=|0+3|=3 \quad\text{so }(0,3) \text{ is on the graph}, \]
\[ f(-2)=|-2+3|=1 \quad\text{so }(-2,1) \text{ is on the graph}, \]
\[ f(-4)=|-4+3|=1 \quad\text{so }(-4,1) \text{ is on the graph}. \]
These are consistent with a V whose vertex is at (-3,0) and symmetric about the vertical line x = -3. - State domain and range.Domain: all real numbers, written \(\mathbb{R}\).
Range: all real y with y \ge 0, written [0, \infty). - Conclusion — which graph represents f(x)=|x+3|?The correct graph is the V-shaped graph with vertex at (-3,0), symmetric about the vertical line x = -3, with the right arm the line y = x + 3 (slope 1) for x \ge -3 and the left arm the line y = -x – 3 (slope -1) for x < -3. It passes through points such as (-4,1), (-2,1), and (0,3), and its y-values are all nonnegative.
See full solution
Graph
Algebra FAQs
What is the vertex of \(f(x)=\lvert x+3\rvert\)?
The vertex is at \(\,-3,0\,\) because \(x+3=0\) when \(x=-3\), giving the minimum value \(0\cdot\)\,.
What shape does the graph have and which way does it open for \(f(x) = \lvert x + 3\rvert\)?
It is a V-shaped graph (absolute value) opening upward, with its point (minimum) at the vertex \( -3,0 \)..
How is \(f(x)=\lvert x+3\rvert\) related to the parent function \(f(x)=\lvert x\rvert\)?
It is the graph of f\(x\) = \(\lvert x\rvert\) shifted left 3 units.
What are the equations and slopes of the two linear pieces of f(x) = \(\lvert x + 3\rvert\) ?
For \(x \ge -3\): \(f(x) = x + 3\) (slope 1). For \(x \le -3\): \(f(x) = -(x + 3)\) (slope -1). Both meet at \((-3,0)\).
What are the domain and range of \(f(x)=\lvert x+3\rvert\)?
Domain: \( (-\infty,\infty) \). Range: \( [0,\infty) \) because absolute value is never negative and minimum value \(0\) occurs at \(x=-3\).
Where are the \(x\)-intercept and \(y\)-intercept of \(f(x)=\lvert x+3\rvert\)?
Where are the \(x\)-intercept and \(y\)-intercept of \(f(x)=\lvert x+3\rvert\)?
Is the graph symmetric, and about which line?
Yes; it is symmetric about the vertical line \(x = -3\) (the axis of symmetry passes through the vertex).
Quick step-by-step: how do I sketch \( f(x) = \lvert x + 3\rvert \)?.
Plot the vertex \((-3,0)\). Draw the right line \(y = x + 3\) for \(x \ge -3\) and the left line \(y = -(x + 3)\) for \(x \le -3\), using slopes \(\pm 1\) to extend the V.
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