Inequality Quadratic Similarity Bd33Fa
1. **State the problem:**
a. Write down the inequality shown on the number line with an open circle at -3 and a closed circle at 2 connected by a solid line.
b. Solve the quadratic equation $5x^2 - 13x - 12 = 0$ using the quadratic formula and give answers correct to 2 decimal places.
c. Given two mathematically similar solids with volumes 416 cm$^3$ (large) and 52 cm$^3$ (small), and the total surface area of the small solid is 60 cm$^2$, find the total surface area of the large solid.
2. **Part a: Write the inequality**
The open circle at -3 means $x > -3$ (not including -3).
The closed circle at 2 means $x \leq 2$ (including 2).
The solid line connects these points, so the inequality is:
$$-3 < x \leq 2$$
3. **Part b: Solve $5x^2 - 13x - 12 = 0$ using the quadratic formula**
The quadratic formula is:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=5$, $b=-13$, and $c=-12$.
Calculate the discriminant:
$$\Delta = b^2 - 4ac = (-13)^2 - 4 \times 5 \times (-12) = 169 + 240 = 409$$
Calculate the square root:
$$\sqrt{409} \approx 20.2237$$
Find the two solutions:
$$x_1 = \frac{13 + 20.2237}{2 \times 5} = \frac{33.2237}{10} = 3.32$$
$$x_2 = \frac{13 - 20.2237}{10} = \frac{-7.2237}{10} = -0.72$$
Rounded to 2 decimal places:
$$x = 3.32 \quad \text{or} \quad x = -0.72$$
4. **Part c: Calculate the total surface area of the large solid**
Since the solids are mathematically similar, the ratio of volumes is related to the scale factor $k$ by:
$$\frac{V_{large}}{V_{small}} = k^3$$
Calculate $k$:
$$k^3 = \frac{416}{52} = 8 \implies k = \sqrt[3]{8} = 2$$
The surface area scales as the square of the scale factor:
$$\frac{A_{large}}{A_{small}} = k^2 = 2^2 = 4$$
Given $A_{small} = 60$ cm$^2$, find $A_{large}$:
$$A_{large} = 4 \times 60 = 240 \text{ cm}^2$$
**Final answers:**
- a. $$-3 < x \leq 2$$
- b. $$x = 3.32 \text{ or } x = -0.72$$
- c. $$240 \text{ cm}^2$$