1. **State the problem:** Solve the equation $$4x - 9 + 9x + 6 = 7x^2 - 3x - 54$$ for $x$.
2. **Combine like terms on the left side:**
$$4x - 9 + 9x + 6 = (4x + 9x) + (-9 + 6) = 13x - 3$$
So the equation becomes:
$$13x - 3 = 7x^2 - 3x - 54$$
3. **Bring all terms to one side to set the equation to zero:**
$$0 = 7x^2 - 3x - 54 - 13x + 3$$
Simplify the right side:
$$0 = 7x^2 - 16x - 51$$
4. **Use the quadratic formula to solve for $x$:**
The quadratic formula is:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=7$, $b=-16$, and $c=-51$.
5. **Calculate the discriminant:**
$$\Delta = b^2 - 4ac = (-16)^2 - 4 \times 7 \times (-51) = 256 + 1428 = 1684$$
6. **Calculate the square root of the discriminant:**
$$\sqrt{1684} = 2\sqrt{421}$$ (since $1684 = 4 \times 421$)
7. **Write the solutions:**
$$x = \frac{-(-16) \pm 2\sqrt{421}}{2 \times 7} = \frac{16 \pm 2\sqrt{421}}{14}$$
8. **Simplify the fraction by canceling 2:**
$$x = \frac{\cancel{2}(8 \pm \sqrt{421})}{\cancel{2}7} = \frac{8 \pm \sqrt{421}}{7}$$
9. **Approximate the solutions:**
$$\sqrt{421} \approx 20.518$$
So,
$$x_1 = \frac{8 + 20.518}{7} = \frac{28.518}{7} \approx 4.074$$
$$x_2 = \frac{8 - 20.518}{7} = \frac{-12.518}{7} \approx -1.788$$
10. **Check which option matches:**
Options given are:
- Option 2: $\frac{28}{3} \approx 9.333$ (no)
- Option 3: $\frac{11}{2} = 5.5$ (no)
- Option 4: $\frac{64}{13} \approx 4.923$ (closest to $4.074$ but not exact)
- Option 1: $\emptyset$ (no solution)
None of the options exactly match the solutions, so the solution set is:
$$\left\{ \frac{8 + \sqrt{421}}{7}, \frac{8 - \sqrt{421}}{7} \right\}$$
Quadratic Equation 93A07A
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