System Inequalities 7Ab 695B46
1. **State the problem:** Solve the system of inequalities for problem 7 parts a) and b).
2. **Problem 7a:**
\[ \frac{9 - x^2}{x} \geq 0 \quad \text{and} \quad 2x - 1 \geq 0 \]
3. **Analyze the first inequality:**
\[ \frac{9 - x^2}{x} \geq 0 \]
The numerator is \(9 - x^2 = (3 - x)(3 + x)\).
The denominator is \(x\).
4. **Find critical points:**
Numerator zeros: \(x = 3, -3\)
Denominator zero: \(x = 0\) (excluded from domain)
5. **Sign analysis intervals:**
- \(( -\infty, -3 )\)
- \(( -3, 0 )\)
- \(( 0, 3 )\)
- \(( 3, \infty )\)
6. **Test signs in each interval:**
- For \(x < -3\), numerator \(9 - x^2 < 0\), denominator \(x < 0\), fraction positive.
- For \(-3 < x < 0\), numerator \(9 - x^2 > 0\), denominator \(x < 0\), fraction negative.
- For \(0 < x < 3\), numerator \(9 - x^2 > 0\), denominator \(x > 0\), fraction positive.
- For \(x > 3\), numerator \(9 - x^2 < 0\), denominator \(x > 0\), fraction negative.
7. **Include points where fraction is zero:**
At \(x = -3\) and \(x = 3\), numerator zero, fraction zero, satisfies \(\geq 0\).
At \(x = 0\), undefined.
8. **Solution for first inequality:**
\[ (-\infty, -3] \cup (0, 3] \]
9. **Second inequality:**
\[ 2x - 1 \geq 0 \implies x \geq \frac{1}{2} \]
10. **Combine both inequalities:**
Intersection of \( (-\infty, -3] \cup (0, 3] \) and \( [\frac{1}{2}, \infty) \) is \( [\frac{1}{2}, 3] \).
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11. **Problem 7b:**
\[ \frac{(x + 5)(x - 1)}{x} \geq 0 \quad \text{and} \quad 10x - 1 < 0 \]
12. **Analyze first inequality:**
Zeros of numerator: \(x = -5, 1\)
Zero of denominator: \(x = 0\) (excluded)
13. **Intervals for sign analysis:**
\( (-\infty, -5), (-5, 0), (0, 1), (1, \infty) \)
14. **Test signs:**
- For \(x < -5\): numerator positive (both factors negative), denominator negative, fraction negative.
- For \(-5 < x < 0\): numerator negative (one factor positive, one negative), denominator negative, fraction positive.
- For \(0 < x < 1\): numerator negative, denominator positive, fraction negative.
- For \(x > 1\): numerator positive, denominator positive, fraction positive.
15. **Include zeros where fraction is zero:**
At \(x = -5\) and \(x = 1\), numerator zero, fraction zero, satisfies \(\geq 0\).
At \(x = 0\), undefined.
16. **Solution for first inequality:**
\[ [-5, 0) \cup [1, \infty) \]
17. **Second inequality:**
\[ 10x - 1 < 0 \implies x < \frac{1}{10} \]
18. **Combine both inequalities:**
Intersection of \( [-5, 0) \cup [1, \infty) \) and \( (-\infty, \frac{1}{10}) \) is \( [-5, 0) \).
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19. **Final answers:**
- For 7a: \( x \in [\frac{1}{2}, 3] \)
- For 7b: \( x \in [-5, 0) \)
20. **Summary:**
We solved each inequality by finding critical points, testing signs, and combining with the second inequality in each system.