1. **Stating the problem:**
We have a rectangle where the length $L$ exceeds the width $W$ by 3 cm, i.e., $L = W + 3$. The area $A$ of the rectangle must not exceed 30 cm$^2$, so $A \leq 30$.
2. **Formula used:**
The area of a rectangle is given by:
$$A = L \times W$$
Since $L = W + 3$, substitute to get:
$$A = W(W + 3)$$
3. **Set up the inequality:**
$$W(W + 3) \leq 30$$
which expands to:
$$W^2 + 3W \leq 30$$
4. **Rewrite the inequality:**
$$W^2 + 3W - 30 \leq 0$$
5. **Solve the quadratic inequality:**
First, solve the quadratic equation:
$$W^2 + 3W - 30 = 0$$
Using the quadratic formula:
$$W = \frac{-3 \pm \sqrt{3^2 - 4 \times 1 \times (-30)}}{2 \times 1} = \frac{-3 \pm \sqrt{9 + 120}}{2} = \frac{-3 \pm \sqrt{129}}{2}$$
6. **Calculate the roots:**
$$\sqrt{129} \approx 11.36$$
So,
$$W_1 = \frac{-3 + 11.36}{2} = \frac{8.36}{2} = 4.18$$
$$W_2 = \frac{-3 - 11.36}{2} = \frac{-14.36}{2} = -7.18$$
7. **Determine the valid range for $W$:**
Since width cannot be negative, discard $W_2 = -7.18$.
The quadratic opens upwards (positive leading coefficient), so the inequality $W^2 + 3W - 30 \leq 0$ holds between the roots.
Thus,
$$-7.18 \leq W \leq 4.18$$
Only positive widths make sense, so:
$$0 < W \leq 4.18$$
8. **Find the corresponding length $L$:**
$$L = W + 3$$
So,
$$L \leq 4.18 + 3 = 7.18$$
**Final answer:**
The width $W$ must be at most approximately 4.18 cm, and the length $L$ at most approximately 7.18 cm, to ensure the area does not exceed 30 cm$^2$.
Rectangle Area Adbbe1
Step-by-step solutions with LaTeX - clean, fast, and student-friendly.