1. **State the problem:** Solve the equation $-4b (3b - 5b - 7) = -5 (2b + 9) + 8$ for $b$.
2. **Simplify inside parentheses:**
$$3b - 5b - 7 = (3b - 5b) - 7 = -2b - 7$$
3. **Rewrite the equation:**
$$-4b(-2b - 7) = -5(2b + 9) + 8$$
4. **Distribute terms:**
$$-4b \times -2b = 8b^2, \quad -4b \times -7 = 28b$$
$$-5 \times 2b = -10b, \quad -5 \times 9 = -45$$
So the equation becomes:
$$8b^2 + 28b = -10b - 45 + 8$$
5. **Combine like terms on the right:**
$$-10b - 45 + 8 = -10b - 37$$
6. **Bring all terms to one side:**
$$8b^2 + 28b + 10b + 37 = 0$$
7. **Combine like terms:**
$$8b^2 + 38b + 37 = 0$$
8. **Use quadratic formula:**
The quadratic formula is:
$$b = \frac{-B \pm \sqrt{B^2 - 4AC}}{2A}$$
where $A=8$, $B=38$, and $C=37$.
9. **Calculate discriminant:**
$$\Delta = B^2 - 4AC = 38^2 - 4 \times 8 \times 37 = 1444 - 1184 = 260$$
10. **Calculate roots:**
$$b = \frac{-38 \pm \sqrt{260}}{16}$$
11. **Simplify square root:**
$$\sqrt{260} = \sqrt{4 \times 65} = 2\sqrt{65}$$
12. **Final solution:**
$$b = \frac{-38 \pm 2\sqrt{65}}{16} = \frac{-19 \pm \sqrt{65}}{8}$$
**Answer:**
$$b = \frac{-19 + \sqrt{65}}{8} \quad \text{or} \quad b = \frac{-19 - \sqrt{65}}{8}$$
Solve Quadratic 588045
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