1. **State the problem:** A rectangular lawn measures 8 meters by 4 meters and is surrounded by a flower bed of uniform width $x$ meters. The total area of the lawn plus the flower bed is 165 square meters. We need to find the width $x$ of the flower bed.
2. **Set up the equation:** The total length including the flower bed is $8 + 2x$ and the total width is $4 + 2x$ because the flower bed surrounds all sides.
3. **Write the area equation:**
$$\text{Total area} = (8 + 2x)(4 + 2x) = 165$$
4. **Expand the product:**
$$ (8 + 2x)(4 + 2x) = 8 \times 4 + 8 \times 2x + 2x \times 4 + 2x \times 2x = 32 + 16x + 8x + 4x^2 $$
5. **Simplify:**
$$ 4x^2 + 24x + 32 = 165 $$
6. **Bring all terms to one side:**
$$ 4x^2 + 24x + 32 - 165 = 0 $$
$$ 4x^2 + 24x - 133 = 0 $$
7. **Divide entire equation by 4 to simplify:**
$$ \frac{\cancel{4}x^2}{\cancel{4}} + \frac{24x}{4} - \frac{133}{4} = 0 $$
$$ x^2 + 6x - \frac{133}{4} = 0 $$
8. **Use quadratic formula:** For $ax^2 + bx + c = 0$,
$$ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} $$
Here, $a=1$, $b=6$, $c=-\frac{133}{4}$.
9. **Calculate discriminant:**
$$ b^2 - 4ac = 6^2 - 4 \times 1 \times \left(-\frac{133}{4}\right) = 36 + 133 = 169 $$
10. **Calculate roots:**
$$ x = \frac{-6 \pm \sqrt{169}}{2} = \frac{-6 \pm 13}{2} $$
11. **Find possible values:**
- $$ x = \frac{-6 + 13}{2} = \frac{7}{2} = 3.5 $$
- $$ x = \frac{-6 - 13}{2} = \frac{-19}{2} = -9.5 $$
12. **Interpret solution:** Width cannot be negative, so $x = 3.5$ meters.
**Final answer:** The width of the flower bed is **3.5 meters**.
Flower Bed Width Fae021
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