1. **State the problem:** Solve the equation $$30 = 18x - 2x^2$$ for $x$.
2. **Rewrite the equation:** Move all terms to one side to set the equation to zero:
$$0 = 18x - 2x^2 - 30$$
which can be rewritten as
$$-2x^2 + 18x - 30 = 0$$
3. **Simplify the equation:** Divide the entire equation by $-2$ to simplify coefficients:
$$0 = \cancel{-2}x^2 - \cancel{18}x + \cancel{30} \div -2$$
which gives
$$x^2 - 9x + 15 = 0$$
4. **Use the quadratic formula:** For an equation $ax^2 + bx + c = 0$, the solutions are
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
Here, $a=1$, $b=-9$, and $c=15$.
5. **Calculate the discriminant:**
$$\Delta = b^2 - 4ac = (-9)^2 - 4(1)(15) = 81 - 60 = 21$$
6. **Find the roots:**
$$x = \frac{-(-9) \pm \sqrt{21}}{2(1)} = \frac{9 \pm \sqrt{21}}{2}$$
7. **Final answer:**
$$x = \frac{9 + \sqrt{21}}{2} \quad \text{or} \quad x = \frac{9 - \sqrt{21}}{2}$$
These are the two solutions to the equation.
Solve Quadratic 4077B1
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