Inequality Quadratic Similarity 629A62
1. **State the problem:**
(a) Write down the inequality shown on the graph.
(b) Use the quadratic formula to solve the equation $$5x^2 - 13x - 12 = 0$$ and give answers correct to 2 decimal places.
(c) Calculate the total surface area of the large solid given the volumes and surface area of the small solid.
2. **Part (a) - Inequality from graph:**
The graph shows a line segment from $$x = -3$$ (open circle, not included) to $$x = 2$$ (closed circle, included).
So the inequality is:
$$-3 < x \leq 2$$
3. **Part (b) - Quadratic formula:**
The quadratic formula for solving $$ax^2 + bx + c = 0$$ is:
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
Here, $$a = 5$$, $$b = -13$$, $$c = -12$$.
Calculate the discriminant:
$$\Delta = b^2 - 4ac = (-13)^2 - 4 \times 5 \times (-12) = 169 + 240 = 409$$
Calculate the square root:
$$\sqrt{409} \approx 20.2237$$
Calculate the two roots:
$$x_1 = \frac{13 + 20.2237}{10} = \frac{33.2237}{10} = 3.32$$
$$x_2 = \frac{13 - 20.2237}{10} = \frac{-7.2237}{10} = -0.72$$
4. **Part (c) - Surface area of large solid:**
Since the solids are mathematically similar, the ratio of volumes is related to the cube of the scale factor $$k$$:
$$\frac{V_{large}}{V_{small}} = k^3$$
Given:
$$V_{large} = 416$$
$$V_{small} = 52$$
Calculate $$k$$:
$$k^3 = \frac{416}{52} = 8 \implies k = \sqrt[3]{8} = 2$$
The surface area scales as the square of $$k$$:
$$\frac{A_{large}}{A_{small}} = k^2$$
Given $$A_{small} = 60$$, calculate $$A_{large}$$:
$$A_{large} = 60 \times 2^2 = 60 \times 4 = 240$$
**Final answers:**
(a) $$-3 < x \leq 2$$
(b) $$x = 3.32$$ or $$x = -0.72$$
(c) Total surface area of large solid = $$240$$ cm\textsuperscript{2}