Compound Inequality K C4Cabe
1. **State the problem:** We need to find the value of $k$ such that the compound inequality $$4 - \frac{x}{3} > 3x - k > -13$$ holds true.
2. **Rewrite the compound inequality as two separate inequalities:**
- $$4 - \frac{x}{3} > 3x - k$$
- $$3x - k > -13$$
3. **Solve the first inequality for $k$:**
$$4 - \frac{x}{3} > 3x - k \implies k > 3x - \left(4 - \frac{x}{3}\right) = 3x - 4 + \frac{x}{3} = \frac{9x}{3} + \frac{x}{3} - 4 = \frac{10x}{3} - 4$$
4. **Solve the second inequality for $k$:**
$$3x - k > -13 \implies -k > -13 - 3x \implies k < 3x + 13$$
5. **Combine the inequalities for $k$:**
$$\frac{10x}{3} - 4 < k < 3x + 13$$
6. **Interpretation:** For the compound inequality to hold for all $x$, the interval for $k$ must be valid for all $x$. However, since $k$ depends on $x$ here, to find a fixed $k$ that satisfies the inequality for all $x$, the inequalities must overlap for all $x$.
7. **Find $k$ such that $$\frac{10x}{3} - 4 < 3x + 13$$ for all $x$:**
$$\frac{10x}{3} - 4 < 3x + 13 \implies \frac{10x}{3} - 3x < 13 + 4 \implies \frac{10x - 9x}{3} < 17 \implies \frac{x}{3} < 17 \implies x < 51$$
8. **Since $x$ must be less than 51 for the inequality to hold, the compound inequality holds for $x < 51$. To find $k$ independent of $x$, consider the boundary at $x=51$:**
$$k > \frac{10(51)}{3} - 4 = \frac{510}{3} - 4 = 170 - 4 = 166$$
$$k < 3(51) + 13 = 153 + 13 = 166$$
9. **Therefore, $k$ must satisfy:**
$$166 < k < 166$$
which is impossible unless $k=166$.
10. **Check if $k=166$ satisfies the original inequality:**
At $x=51$, both inequalities become equalities, so $k=166$ is the value that makes the compound inequality hold.
**Final answer:**
$$k = 166$$