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1 | 1 | --- |
2 | 2 | title: Mathematics Week 5 Graded Assignment |
| 3 | +label: Week 5 |
3 | 4 | weight: 5 |
4 | | -tags: |
5 | | -- mathematics |
6 | 5 | categories: |
7 | 6 | - Mathematics Graded Assignment |
8 | | -series: |
9 | | -- Mathematics Graded Assignment |
10 | | -excludeSearch: false |
11 | | -width: wide |
12 | 7 | --- |
13 | 8 |
|
| 9 | +--- |
| 10 | + |
| 11 | +**1. Function Identification via Graph (Figure M1W8A-8.1)** |
| 12 | + |
| 13 | +*Question:* |
| 14 | +A graph is shown in Figure M1W8A-8.1, ◦symbol signifies that the straight line does not touch the point and the - symbol signifies that the line touches the point. |
| 15 | +Choose the correct option. |
| 16 | + |
| 17 | +- The graph cannot be a function, because it fails the vertical line test. |
| 18 | +- The graph cannot be a function, because it passes the horizontal line test but fails the vertical line test. |
| 19 | +- The graph can be a function, because it passes the vertical line test. |
| 20 | +- The graph cannot be a function, because it passes the vertical line test but fails the horizontal line test. |
| 21 | + |
| 22 | +*Solution:* |
| 23 | +To check if the given graph represents a function, use the vertical line test. In Figure M1W8A-8.1, every vertical line crosses the graph only once (including both - and ◦ as per definition). Therefore, the graph represents a function. |
| 24 | + |
| 25 | +- Correct options: |
| 26 | + - The graph can be of a function, because it passes the vertical line test. |
| 27 | + - The graph fails the horizontal line test. |
| 28 | + - The graph represents the graph of neither even function nor odd function. |
| 29 | + - The given graph is not invertible in the given domain. |
| 30 | +- Incorrect options: |
| 31 | + - The graph cannot be of a function, because it passes the vertical line test but fails the horizontal line test. |
| 32 | + - The graph cannot be of a function, because it fails the vertical line test. |
| 33 | + - The graph cannot be of a function, because it passes the horizontal line test but fails the vertical line test. |
| 34 | + - The graph fails the horizontal line test thus it can be an injective function. |
| 35 | + - The graph represents the graph of either even function or odd function.[^1] |
| 36 | + |
| 37 | +--- |
| 38 | + |
| 39 | +**2. Injectivity of Power Functions (Figures M1W8AS-8.1 and M1W8AS-8.2)** |
| 40 | + |
| 41 | +*Question:* |
| 42 | +For \$ y = x^n \$, where \$ n \$ is a positive integer and \$ x \in \mathbb{R} \$, which of the following statement is true? |
| 43 | + |
| 44 | +- For all values of n, y is not a one-to-one function. |
| 45 | +- For all values of n, y is an injective function. |
| 46 | +- y is not a function. |
| 47 | +- If n is an even number, then y is not an injective function. If n is an odd number, then y is an injective function. |
| 48 | + |
| 49 | +*Solution:* |
| 50 | + |
| 51 | +- \$ y = x^n \$ is a function for all positive integers \$ n \$. |
| 52 | +- If \$ n \$ is odd, the function is injective (passes the horizontal line test, see Figure M1W8AS-8.1). |
| 53 | +- If \$ n \$ is even, the function is not injective (see Figure M1W8AS-8.2). |
| 54 | +- Therefore, the correct option is: If n is even, not injective; if n is odd, injective.[^1] |
| 55 | + |
| 56 | +--- |
| 57 | + |
| 58 | +**3. Algebraic Simplification** |
| 59 | + |
| 60 | +*Question:* |
| 61 | +If \$ 4m - n = 0 \$, then the value of |
| 62 | + |
| 63 | +$$ |
| 64 | +\frac{16^m}{2^n} + \frac{27^n}{96^m} |
| 65 | +$$ |
| 66 | + |
| 67 | +is |
| 68 | + |
| 69 | +*Solution:* |
| 70 | +Given \$ 4m - n = 0 \$, |
| 71 | + |
| 72 | +$$ |
| 73 | +\frac{16^m}{2^n} + \frac{27^n}{96^m} |
| 74 | += (2^4)^m / 2^n + (3^3)^n / (2^5 \cdot 3)^m |
| 75 | += 2^{4m-n} + 3^{3n-6m} |
| 76 | += 2^0 + 3^0 = 1 + 1 = 2 |
| 77 | +$$ |
| 78 | + |
| 79 | +**Answer:** 2[^1] |
| 80 | + |
| 81 | +--- |
| 82 | + |
| 83 | +**4. Radioactive Decay (Half-Life Calculation)** |
| 84 | + |
| 85 | +*Question:* |
| 86 | +Half-life of an element is the time required for half of a given sample of radioactive element to change to another element. The rate of change of concentration is calculated by the formula \$ A(t) = A_0 (1/2)^{t/\gamma} \$, where \$ \gamma \$ is the half-life. |
| 87 | +If Radium has a half-life of 1600 years and the initial concentration is 100%, calculate the percentage of Radium after 2000 years. |
| 88 | + |
| 89 | +- 35% |
| 90 | +- 42% |
| 91 | +- 19% |
| 92 | +- 21% |
| 93 | + |
| 94 | +*Solution:* |
| 95 | + |
| 96 | +$$ |
| 97 | +A(2000) = 100 \times (1/2)^{2000/1600} = 100 \times (1/2)^{1.25} \approx 42\% |
| 98 | +$$ |
| 99 | + |
| 100 | +**Answer:** 42%[^1] |
| 101 | + |
| 102 | +--- |
| 103 | + |
| 104 | +**5. Domain of a Composite Function** |
| 105 | + |
| 106 | +*Question:* |
| 107 | +If \$ f(x) = (1 - x)^{1/2} \$ and \$ g(x) = 1 - x^2 \$, find the domain of the composite function \$ g \circ f \$. |
| 108 | + |
| 109 | +- \$ \mathbb{R} \$ |
| 110 | +- \$ (-\infty, 1] \cap [-2, \infty) \cup (-\infty, -2) \$ |
| 111 | +- \$ [1, \infty) \$ |
| 112 | +- \$ \mathbb{R} \setminus (1, \infty) \$ |
| 113 | + |
| 114 | +*Solution:* |
| 115 | + |
| 116 | +- Domain of \$ f(x) \$: \$ x \leq 1 \$ (\$ (-\infty, 1] \$) |
| 117 | +- Domain of \$ g(x) \$: \$ \mathbb{R} \$, but range of \$ f(x) \$ is \$ [0, \infty) \$ |
| 118 | +- So, domain of \$ g \circ f \$ is \$ (-\infty, 1] \$ (options 2 and 4 are correct)[^1] |
| 119 | + |
| 120 | +--- |
| 121 | + |
| 122 | +**6. Domain of the Inverse Function** |
| 123 | + |
| 124 | +*Question:* |
| 125 | +Find the domain of the inverse function of \$ y = x^3 + 1 \$. |
| 126 | + |
| 127 | +- \$ \mathbb{R} \$ |
| 128 | +- \$ \mathbb{R} \setminus \{1\} \$ |
| 129 | +- \$ [1, \infty) \$ |
| 130 | +- \$ \mathbb{R} \setminus [1, \infty) \$ |
| 131 | + |
| 132 | +*Solution:* |
| 133 | +The range of \$ y = x^3 + 1 \$ is \$ \mathbb{R} \$, so the domain of its inverse is also \$ \mathbb{R} \$. |
| 134 | +**Answer:** \$ \mathbb{R} \$[^1] |
| 135 | + |
| 136 | +--- |
| 137 | + |
| 138 | +**7. Intersection Points of a Function and Its Inverse** |
| 139 | + |
| 140 | +*Question:* |
| 141 | +If \$ f(x) = x^3 \$, then which of the following is the set of points where the graphs of \$ f(x) \$ and \$ f^{-1}(x) \$ intersect? |
| 142 | + |
| 143 | +- {(-1, 1), (0, 0), (1, -1)} |
| 144 | +- {(-2, -8), (1, 1), (2, 8)} |
| 145 | +- {(-1, -1), (0, 0), (1, 1)} |
| 146 | +- {(-2, -8), (0, 0), (2, 8)} |
| 147 | + |
| 148 | +*Solution:* |
| 149 | +Solve \$ x^3 = x \Rightarrow x(x^2 - 1) = 0 \Rightarrow x = -1, 0, 1 \$. |
| 150 | +So, intersection points are {(-1, -1), (0, 0), (1, 1)}[^1] |
| 151 | + |
| 152 | +--- |
| 153 | + |
| 154 | +**8. Population Growth Prediction** |
| 155 | + |
| 156 | +*Question:* |
| 157 | +In a survey, population growth is given by \$ \alpha(T) = \alpha_0 (1 + d/100)^T \$. If in 2015, the population of Adyar was 30,000 and the growth rate is 4% per year, what will be the approximate population in 2020? |
| 158 | + |
| 159 | +- 60251 |
| 160 | +- 71255 |
| 161 | +- 91000 |
| 162 | +- 36500 |
| 163 | + |
| 164 | +*Solution:* |
| 165 | +\$ T = 5 \$, \$ \alpha(5) = 30000 \times (1.04)^5 \approx 36500 \$[^1] |
| 166 | + |
| 167 | +--- |
| 168 | + |
| 169 | +**9. Reflection of a Function Across \$ y = x \$ (Figure M1W8AS-8.3)** |
| 170 | + |
| 171 | +*Question:* |
| 172 | +An ant moves along \$ f(x) = x^2 + 1 \$ for \$ x \in [0, \infty) \$. A mirror is placed along \$ y = x \$. If the reflection moves along \$ g(x) \$, which is/are correct? |
| 173 | + |
| 174 | +- \$ g(x) = f^{-1}(x) \$ |
| 175 | +- \$ g(x) = f(x) \$ |
| 176 | +- \$ g(x) = \sqrt{x-1} \$ |
| 177 | +- \$ g(x) = \sqrt{x+1} \$ |
| 178 | + |
| 179 | +*Solution:* |
| 180 | +The reflection is the inverse function, so \$ g(x) = f^{-1}(x) = \sqrt{x-1} \$. |
| 181 | +Correct options: 1 and 3[^1] |
| 182 | + |
| 183 | +--- |
| 184 | + |
| 185 | +**10. Festival Discount Offers (Applied Math)** |
| 186 | + |
| 187 | +*Question:* |
| 188 | +A textile shop offers: |
| 189 | +D1: Shop for more than ₹14,999 and pay only ₹9,999. |
| 190 | +D2: Avail 30% discount on the total payable amount. |
| 191 | +If Shalini buys two dresses, each over ₹8,000, and can use both offers, which is/are correct? |
| 192 | + |
| 193 | +- The minimum amount she should pay after applying two offers cannot be determined because the exact values are unknown. |
| 194 | +- The minimum amount she should pay after applying both offers is approximately ₹6,999. |
| 195 | +- The amount after D2 only is approximately ₹11,199. |
| 196 | +- The amount after D1 only is approximately ₹9,999. |
| 197 | +- If total is ₹17,999, to pay minimum, avail D1 first, then D2. |
| 198 | +- If total is ₹17,999, availing D2 first, then D1 is not possible. |
| 199 | +- If total is ₹17,999, to pay minimum, avail D2 first, then D1. |
| 200 | + |
| 201 | +*Solution:* |
| 202 | + |
| 203 | +- If D1 first, then D2: ₹9,999 × 0.7 = ₹6,999 (minimum). |
| 204 | +- If D2 first, amount may fall below ₹14,999, so D1 may not be applicable. |
| 205 | +- D1 only: ₹9,999. |
| 206 | +- D2 only: ₹17,999 × 0.7 = ₹12,599 (if total is ₹17,999). |
| 207 | +- So, correct: 2, 4, 5, 6[^1] |
| 208 | + |
| 209 | +--- |
| 210 | + |
| 211 | +**11. Injectivity and Function Operations** |
| 212 | + |
| 213 | +*Question:* |
| 214 | +If \$ f(x) = x^2 \$ and \$ h(x) = x-1 \$, which options are incorrect? |
| 215 | + |
| 216 | +- \$ f \circ h \$ is not injective. |
| 217 | +- \$ f \circ h \$ is injective. |
| 218 | +- \$ f(f(h(x))) \times h(x) = (x-1)^4 \$ |
| 219 | +- \$ f(f(h(x))) \times h(x) = (x-1)^5 \$ |
| 220 | + |
| 221 | +*Solution:* |
| 222 | + |
| 223 | +- \$ f \circ h = (x-1)^2 \$ is not injective. |
| 224 | +- \$ f(f(h(x))) \times h(x) = ((x-1)^2)^2 \times (x-1) = (x-1)^5 \$. |
| 225 | +- So, incorrect: 2 and 3[^1] |
| 226 | + |
| 227 | +--- |
| 228 | + |
| 229 | +**12. Graphical Properties and Inverses (Figure 3)** |
14 | 230 |
|
15 | | -1. |
| 231 | +*Question:* |
| 232 | +Let \$ f(x), g(x), p(x), q(x) \$ be functions defined on \$ \mathbb{R} \$. Refer Figure 3 (A and B) and choose correct options: |
16 | 233 |
|
17 | | -{{< border >}} |
| 234 | +- \$ g(x) \$ may be the inverse of \$ f(x) \$. |
| 235 | +- \$ p(x) \$ and \$ q(x) \$ are even functions but \$ f(x) \$ and \$ g(x) \$ are neither even nor odd. |
| 236 | +- \$ q(x) \$ could not be the inverse function of \$ p(x) \$. |
| 237 | +- \$ p(x), q(x) \$ can be even degree polynomials and \$ f(x) \$ can be an odd degree polynomial. |
18 | 238 |
|
19 | | -To determine which statements about the function \$ y = x^n \$ (where \$ n \$ is a positive integer and \$ x \in \mathbb{R} \$) are true, we analyze its injectivity based on whether \$ n \$ is even or odd: |
| 239 | +*Solution:* |
20 | 240 |
|
21 | | -1. **Statement 1**: "For all values of \$ n \$, \$ y \$ is not a one-to-one function." |
22 | | -**False**. When \$ n \$ is odd, \$ y = x^n \$ is injective (one-to-one) over \$ \mathbb{R} \$. |
23 | | -2. **Statement 2**: "For all values of \$ n \$, \$ y \$ is an injective function." |
24 | | -**False**. For even \$ n \$, \$ y = x^n \$ is **not** injective (e.g., \$ x = 2 \$ and \$ x = -2 \$ both map to \$ y = 16 \$ when \$ n = 4 \$). |
25 | | -3. **Statement 3**: "\$ y \$ is not a function." |
26 | | -**False**. \$ y = x^n \$ is a valid function, as every \$ x \in \mathbb{R} \$ maps to exactly one \$ y \$. |
27 | | -4. **Statement 4**: "If \$ n \$ is an even number, then \$ y \$ is not an injective function." |
28 | | -**True**. For even \$ n \$, distinct inputs like \$ x \$ and \$ -x \$ produce the same output (e.g., \$ 2^2 = (-2)^2 = 4 \$), violating injectivity. |
29 | | -5. **Statement 5**: "If \$ n \$ is an odd number, then \$ y \$ is an injective function." |
30 | | -**True**. For odd \$ n \$, \$ y = x^n \$ preserves the sign and uniqueness of inputs (e.g., \$ 2^3 = 8 \$, \$ (-2)^3 = -8 \$), ensuring injectivity. |
| 241 | +- \$ f(x) \$ and \$ g(x) \$ are symmetric across \$ y = x \$, so \$ g(x) \$ may be inverse of \$ f(x) \$. |
| 242 | +- \$ p(x) \$ and \$ q(x) \$ are symmetric about the y-axis, so they are even functions. |
| 243 | +- \$ q(x) \$ is not symmetric across \$ y = x \$, so cannot be inverse of \$ p(x) \$. |
| 244 | +- End behaviors suggest \$ p(x), q(x) \$ can be even degree polynomials, \$ f(x) \$ can be odd degree. |
| 245 | +- All options (a), (b), (c), (d) are correct[^1] |
31 | 246 |
|
32 | 247 | --- |
33 | 248 |
|
34 | | -**Final Answer:** |
| 249 | +**Note:** For all questions involving graphs, the referenced figures (e.g., Figure M1W8A-8.1, M1W8AS-8.1, etc.) are described in the solutions, but the actual images are not included in this text extraction. The reasoning is based on their descriptions in the PDF.[^1] |
35 | 250 |
|
36 | | -$\boxed{ Statements 4 and 5 are true. }$ |
| 251 | +<div style="text-align: center">⁂</div> |
37 | 252 |
|
38 | | -$\boxed{3}$ |
| 253 | +[^1]: week-5.pdf |
39 | 254 |
|
40 | | -{{< /border >}} |
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