Absolute Value Sum 3A74E2
1. **State the problem:** Solve the equation $$|3x + 2| + |3x - 2| = 5$$ for $x$.
2. **Understand the absolute value:** The absolute value function $|a|$ equals $a$ if $a \geq 0$ and $-a$ if $a < 0$.
3. **Identify critical points:** The expressions inside the absolute values change sign at points where $3x + 2 = 0$ and $3x - 2 = 0$.
- Solve $3x + 2 = 0 \Rightarrow x = -\frac{2}{3}$
- Solve $3x - 2 = 0 \Rightarrow x = \frac{2}{3}$
4. **Break the real line into intervals based on these points:**
- Interval 1: $x < -\frac{2}{3}$
- Interval 2: $-\frac{2}{3} \leq x < \frac{2}{3}$
- Interval 3: $x \geq \frac{2}{3}$
5. **Solve on each interval:**
- **Interval 1 ($x < -\frac{2}{3}$):**
Here, $3x + 2 < 0$ and $3x - 2 < 0$, so
$$|3x + 2| = -(3x + 2) = -3x - 2$$
$$|3x - 2| = -(3x - 2) = -3x + 2$$
Substitute into the equation:
$$-3x - 2 + (-3x + 2) = 5$$
Simplify:
$$-3x - 2 - 3x + 2 = 5$$
$$-6x = 5$$
$$x = -\frac{5}{6}$$
Check if $x = -\frac{5}{6}$ lies in Interval 1 ($x < -\frac{2}{3} \approx -0.666$):
Since $-\frac{5}{6} = -0.833 < -0.666$, it is valid.
- **Interval 2 ($-\frac{2}{3} \leq x < \frac{2}{3}$):**
Here, $3x + 2 \geq 0$ and $3x - 2 < 0$, so
$$|3x + 2| = 3x + 2$$
$$|3x - 2| = -(3x - 2) = -3x + 2$$
Substitute:
$$(3x + 2) + (-3x + 2) = 5$$
Simplify:
$$3x + 2 - 3x + 2 = 5$$
$$4 = 5$$
This is false, so no solution in Interval 2.
- **Interval 3 ($x \geq \frac{2}{3}$):**
Here, $3x + 2 \geq 0$ and $3x - 2 \geq 0$, so
$$|3x + 2| = 3x + 2$$
$$|3x - 2| = 3x - 2$$
Substitute:
$$(3x + 2) + (3x - 2) = 5$$
Simplify:
$$3x + 2 + 3x - 2 = 5$$
$$6x = 5$$
$$x = \frac{5}{6}$$
Check if $x = \frac{5}{6}$ lies in Interval 3 ($x \geq \frac{2}{3} \approx 0.666$):
Since $\frac{5}{6} = 0.833 > 0.666$, it is valid.
6. **Final solutions:**
$$x = -\frac{5}{6} \quad \text{and} \quad x = \frac{5}{6}$$