1. **State the problem:** Solve the quadratic equation $$-3x^2 + 8x - 7 = 0$$ using the quadratic formula.
2. **Quadratic formula:** For an equation $$ax^2 + bx + c = 0$$, the solutions are given by:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
3. **Identify coefficients:** Here, $$a = -3$$, $$b = 8$$, and $$c = -7$$.
4. **Fill in the quadratic formula:**
$$x = \frac{-8 \pm \sqrt{8^2 - 4(-3)(-7)}}{2(-3)}$$
5. **Simplify inside the square root:**
$$8^2 = 64$$
$$4 \times (-3) \times (-7) = 84$$
6. **Calculate the discriminant:**
$$64 - 84 = -20$$
7. **Rewrite the formula with the discriminant:**
$$x = \frac{-8 \pm \sqrt{-20}}{-6}$$
8. **Simplify the square root of a negative number:**
$$\sqrt{-20} = \sqrt{-1 \times 20} = i\sqrt{20} = i \times 2\sqrt{5}$$
9. **Substitute back:**
$$x = \frac{-8 \pm 2i\sqrt{5}}{-6}$$
10. **Simplify the fraction by dividing numerator and denominator by 2:**
$$x = \frac{\cancel{-8} \pm \cancel{2}i\sqrt{5}}{\cancel{-6}} = \frac{-4 \pm i\sqrt{5}}{-3}$$
11. **Simplify signs:** Dividing numerator and denominator by -1:
$$x = \frac{4 \mp i\sqrt{5}}{3}$$
12. **Final solution set:**
$$x = \left\{ \frac{4 \pm i\sqrt{5}}{3} \right\}$$
13. **Match with options:** Option A matches the solution.
**Answer:**
(a) $$x = \frac{-8 \pm \sqrt{8^2 - 4(-3)(-7)}}{2(-3)}$$
(b) The correct solution is option A: $$x = \left\{ \frac{4 \pm i\sqrt{5}}{3} \right\}$$
Quadratic Formula 56Ef79
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.