If the domain of the function f(x) = log_e left(frac2x + 34x^2 + x - 3right) + cos^-1left(frac2x - 1x + 2right)$f(x) = \log_e \left(\frac{2x + 3}{4x^2 + x - 3}\right) + \cos^{-1}\left(\frac{2x - 1}{x + 2}\right)$ is (alpha, beta]$(\alpha, \beta]$ , then the value of 5beta - 4alpha$5\beta - 4\alpha$ is equal to
A.10$10$
B.12$12$
C.11$11$
D.9$9$
Solution & Explanation
### Related Formula
textDomain of log_e(A): A gt 0$\text{Domain of } \log_e(A): A \gt 0$textDomain of cos^-1(B): -1 le B le 1$\text{Domain of } \cos^{-1}(B): -1 \le B \le 1$
### Core Logic
Condition 1: Logarithm domain
frac2x + 34x^2 + x - 3 gt 0$\frac{2x + 3}{4x^2 + x - 3} \gt 0$
Factorizing the denominator: 4x^2 + 4x - 3x - 3 = 4x(x+1) - 3(x+1) = (4x-3)(x+1)$4x^2 + 4x - 3x - 3 = 4x(x+1) - 3(x+1) = (4x-3)(x+1)$.
frac2x + 3(4x - 3)(x + 1) gt 0$\frac{2x + 3}{(4x - 3)(x + 1)} \gt 0$
Critical points are x = -frac32, -1, frac34$x = -\frac{3}{2}, -1, \frac{3}{4}$. Using the wavy curve method:
The intervals where it is positive are left(-frac32, -1right) cup left(frac34, inftyright)$\left(-\frac{3}{2}, -1\right) \cup \left(\frac{3}{4}, \infty\right)$. Let this be set D_1$D_1$.
### Step 1: Inverse Trigonometric Domain
Condition 2: Arc cosine domain
-1 le frac2x - 1x + 2 le 1$-1 \le \frac{2x - 1}{x + 2} \le 1$
This breaks into two inequalities:
(i) frac2x - 1x + 2 ge -1 Rightarrow frac2x - 1x + 2 + 1 ge 0 Rightarrow frac3x + 1x + 2 ge 0$\frac{2x - 1}{x + 2} \ge -1 \Rightarrow \frac{2x - 1}{x + 2} + 1 \ge 0 \Rightarrow \frac{3x + 1}{x + 2} \ge 0$
Critical points are x = -2, -frac13$x = -2, -\frac{1}{3}$. The valid set is (-infty, -2) cup left[-frac13, inftyright)$(-\infty, -2) \cup \left[-\frac{1}{3}, \infty\right)$.
(ii) frac2x - 1x + 2 le 1 Rightarrow frac2x - 1x + 2 - 1 le 0 Rightarrow fracx - 3x + 2 le 0$\frac{2x - 1}{x + 2} \le 1 \Rightarrow \frac{2x - 1}{x + 2} - 1 \le 0 \Rightarrow \frac{x - 3}{x + 2} \le 0$
Critical points are x = -2, 3$x = -2, 3$. The valid set is (-2, 3]$(-2, 3]$.
Intersection for the cosine domain (D_2$D_2$): (-2, 3] cap left( (-infty, -2) cup left[-frac13, inftyright) right) = left[-frac13, 3right]$(-2, 3] \cap \left( (-\infty, -2) \cup \left[-\frac{1}{3}, \infty\right) \right) = \left[-\frac{1}{3}, 3\right]$.
### Step 2: Finding Total Domain
Total domain D = D_1 cap D_2$D = D_1 \cap D_2$:
D = left( left(-frac32, -1right) cup left(frac34, inftyright) right) cap left[-frac13, 3right]$D = \left( \left(-\frac{3}{2}, -1\right) \cup \left(\frac{3}{4}, \infty\right) \right) \cap \left[-\frac{1}{3}, 3\right]$
Since left[-frac13, 3right]$\left[-\frac{1}{3}, 3\right]$ starts strictly greater than -1$-1$, the overlap with left(-frac32, -1right)$\left(-\frac{3}{2}, -1\right)$ is empty.
Overlap with left(frac34, inftyright)$\left(\frac{3}{4}, \infty\right)$ occurs from frac34$\frac{3}{4}$ to 3$3$.
Thus, D = left(frac34, 3right]$D = \left(\frac{3}{4}, 3\right]$.
### Step 3: Calculating Final Expression
Comparing with (alpha, beta]$(\alpha, \beta]$:
alpha = frac34$\alpha = \frac{3}{4}$ and beta = 3$\beta = 3$.
We need to find 5beta - 4alpha$5\beta - 4\alpha$:
5(3) - 4left(frac34right) = 15 - 3 = 12$5(3) - 4\left(\frac{3}{4}\right) = 15 - 3 = 12$
### Pattern Recognition
Compound domains always require individual set resolution (using Wavy Curve) followed by taking the strictest absolute intersection. Identifying disjoint segments (like x lt -1$x \lt -1$ missing the cosine bound) prunes manual checking.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Maths: Functions
Keywords:#Function domain calculation#JEE Main 2024 Evening Q18#Functions JEE Main 2024#Domain and Range JEE Main 2024
More Functions Previous-Year Questions — Page 9
Q12jee_main_2024_30_jan_morningDomain and Range
If the domain of the functionf(x) = cos^-1left(frac2 - |x|4right) + (log_e (3 - x))^-1$f(x) = \cos^{-1}\left(\frac{2 - |x|}{4}\right) + (\log_e (3 - x))^{-1}$
is [-alpha, beta) - \gamma\$[-\alpha, \beta) - \{\gamma\}$, then alpha + beta + gamma$\alpha + \beta + \gamma$ is equal to:
A.12$12$
B.9$9$
C.11$11$
D.8$8$
Solution
### Related Formula
-1 leq textargument of cos^-1 leq 1$-1 \leq \text{argument of } \cos^{-1} \leq 1$log_a x text is defined for x > 0 text and base a > 0, a neq 1$\log_a x \text{ is defined for } x > 0 \text{ and base } a > 0, a \neq 1$f^-1 text signifies denominator neq 0$f^{-1} \text{ signifies denominator } \neq 0$
### Core Logic
For f(x)$f(x)$ to be defined, both terms must be defined independently.
Term 1: cos^-1left(frac2 - |x|4right)$\cos^{-1}\left(\frac{2 - |x|}{4}\right)$
The domain requires:
-1 leq frac2 - |x|4 leq 1$-1 \leq \frac{2 - |x|}{4} \leq 1$-4 leq 2 - |x| leq 4$-4 \leq 2 - |x| \leq 4$-6 leq -|x| leq 2$-6 \leq -|x| \leq 2$-2 leq |x| leq 6$-2 \leq |x| \leq 6$
Since |x|$|x|$ is always non-negative, the valid condition reduces to |x| leq 6$|x| \leq 6$.
This implies x in [-6, 6] quad dots (1)$x \in [-6, 6] \quad \dots (1)$
### Step 1: Domain of logarithmic term
Term 2: (log_e(3 - x))^-1 = frac1log_e(3 - x)$(\log_e(3 - x))^{-1} = \frac{1}{\log_e(3 - x)}$
The argument of the logarithm must be positive:
3 - x > 0 Rightarrow x < 3 quad dots (2)$3 - x > 0 \Rightarrow x < 3 \quad \dots (2)$
Also, the denominator cannot be zero:
log_e(3 - x) neq 0 Rightarrow 3 - x neq 1 Rightarrow x neq 2 quad dots (3)$\log_e(3 - x) \neq 0 \Rightarrow 3 - x \neq 1 \Rightarrow x \neq 2 \quad \dots (3)$
### Step 2: Combining intersection regions
Taking the intersection of (1), (2), and (3):
x in [-6, 6] cap (-infty, 3) cap x neq 2$x \in [-6, 6] \cap (-\infty, 3) \cap x \neq 2$x in [-6, 3) - \2\$x \in [-6, 3) - \{2\}$
Comparing this with the given domain [-alpha, beta) - \gamma\$[-\alpha, \beta) - \{\gamma\}$:
alpha = 6$\alpha = 6$, beta = 3$\beta = 3$, gamma = 2$\gamma = 2$.
### Step 3: Calculating target value
alpha + beta + gamma = 6 + 3 + 2 = 11$\alpha + \beta + \gamma = 6 + 3 + 2 = 11$
### Pattern Recognition
Isolate the constraints of piecewise function composition: inner constraints (argument bounds), denominator zero-checks, and fundamental range boundaries.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Maths: Relations and Functions
Q21jee_main_2024_30_jan_morningSet Operations
A group of 40 students appeared in an examination of 3 subjects - Mathematics, Physics & Chemistry. It was found that all students passed in at least one of the subjects, 20 students passed in Mathematics, 25 students passed in Physics, 16 students passed in Chemistry, at most 11 students passed in both Mathematics and Physics, at most 15 students passed in both Physics and Chemistry, at most 15 students passed in both Mathematics and Chemistry. The maximum number of students passed in all the three subjects is
Numerical Answer.Answer: 10 to 10
Solution
### Related Formula
n(M cup P cup C) = n(M) + n(P) + n(C) - n(M cap P) - n(P cap C) - n(M cap C) + n(M cap P cap C)$n(M \cup P \cup C) = n(M) + n(P) + n(C) - n(M \cap P) - n(P \cap C) - n(M \cap C) + n(M \cap P \cap C)$
### Core Logic
Set Operations diagram for Q21 - JEE Main 2024 Morning
Let x$x$ be the number of students who passed in all three subjects, so n(M cap P cap C) = x$n(M \cap P \cap C) = x$.
We are given:
n(M) = 20, n(P) = 25, n(C) = 16$n(M) = 20, n(P) = 25, n(C) = 16$n(M cup P cup C) = 40$n(M \cup P \cup C) = 40$
Constraints:
n(M cap P) le 11$n(M \cap P) \le 11$n(P cap C) le 15$n(P \cap C) \le 15$n(M cap C) le 15$n(M \cap C) \le 15$
If we let n(M cap P) = 11$n(M \cap P) = 11$, then the region representing only M cap P$M \cap P$ is 11 - x$11 - x$. For this to be non-negative, x le 11$x \le 11$.
### Step 1: Testing x = 11
Set Operations diagram for Q21 - JEE Main 2024 Morning
Assume x = 11$x = 11$.
To maximize, let's fix n(M cap P) = 11$n(M \cap P) = 11$. This leaves 0$0$ students in (M cap P) - (M cap P cap C)$(M \cap P) - (M \cap P \cap C)$.
Let n(M cap C) = 11 + z$n(M \cap C) = 11 + z$ and n(P cap C) = 11 + y$n(P \cap C) = 11 + y$.
Constraints limit these subsets:
11 + z le 15 Rightarrow z le 4$11 + z \le 15 \Rightarrow z \le 4$11 + y le 15 Rightarrow y le 4$11 + y \le 15 \Rightarrow y \le 4$
Filling the Venn diagram nodes:
Only M = 20 - 11 - z - 0 = 9 - z$M = 20 - 11 - z - 0 = 9 - z$
Only P = 25 - 11 - y - 0 = 14 - y$P = 25 - 11 - y - 0 = 14 - y$
Only C = 16 - 11 - y - z = 5 - y - z$C = 16 - 11 - y - z = 5 - y - z$
Summing all disjoint areas:
Total = (9 - z) + 0 + (14 - y) + z + 11 + y + (5 - y - z) = 40$= (9 - z) + 0 + (14 - y) + z + 11 + y + (5 - y - z) = 40$39 - y - z = 40 Rightarrow y + z = -1$39 - y - z = 40 \Rightarrow y + z = -1$
Since subsets cannot be negative, x=11$x=11$ is impossible.
### Step 2: Testing x = 10
Set Operations diagram for Q21 - JEE Main 2024 Morning
Assume x = 10$x = 10$.
Let's construct a valid distribution with x = 10$x = 10$.
We can choose intersection values:
n(M cap P) = 10$n(M \cap P) = 10$, so only M cap P$M \cap P$ is 0$0$.
n(M cap C) = 11$n(M \cap C) = 11$, so only M cap C$M \cap C$ is 1$1$.
n(P cap C) = 10$n(P \cap C) = 10$, so only P cap C$P \cap C$ is 0$0$.
This gives:
Only M = 20 - 10 - 0 - 1 = 9$M = 20 - 10 - 0 - 1 = 9$
Only P = 25 - 10 - 0 - 0 = 15$P = 25 - 10 - 0 - 0 = 15$
Only C = 16 - 10 - 1 - 0 = 5$C = 16 - 10 - 1 - 0 = 5$
Summing up = 9 + 15 + 5 + 0 + 1 + 0 + 10 = 40$9 + 15 + 5 + 0 + 1 + 0 + 10 = 40$.
All conditions are satisfied perfectly.
Hence, the maximum number is 10.
### Pattern Recognition
In multi-constraint Venn diagram maximization, test the theoretical upper bound sequentially downward until a non-negative configuration for all disjoint subsets is achieved.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Maths: Sets
Q24jee_main_2024_30_jan_morningTypes of Functions
Let A = \1, 2, 3, dots, 7\$A = \{1, 2, 3, \dots, 7\}$ and let P(A)$P(A)$ denote the power set of A$A$. If the number of functionsf: A to P(A)$f: A \to P(A)$ such that a in f(a)$a \in f(a)$forall a in A$\forall a \in A$ is m^n$m^n$, m$m$ and n in mathbbN$n \in \mathbb{N}$ and m$m$ is least, then m + n$m + n$ is equal to
Numerical Answer.Answer: 44 to 44
Solution
### Related Formula
textSize of Power Set |P(A)| = 2^|A|$\text{Size of Power Set } |P(A)| = 2^{|A|}$
### Core Logic
For a function f: A to P(A)$f: A \to P(A)$, each element a in A$a \in A$ maps to a subset of A$A$.
The condition is a in f(a)$a \in f(a)$.
This means that the subset assigned to a$a$ must contain the element a$a$.
How many such subsets exist in P(A)$P(A)$?
Since |A| = 7$|A| = 7$, there are 2^7$2^7$ total subsets. Exactly half of these contain a specific element a$a$.
Number of subsets containing 'a' is 2^7-1 = 2^6 = 64$2^{7-1} = 2^6 = 64$.
### Step 1: Calculating total functions
For each element in A$A$ (which has 7 elements), there are independently 2^6$2^6$ choices for its image in P(A)$P(A)$.
Total options for 1 will be 2^6$2^6$.
Similarly, for every other element up to 7.
Hence, total number of functions is:
(2^6) times (2^6) times (2^6) times (2^6) times (2^6) times (2^6) times (2^6) = (2^6)^7 = 2^42$(2^6) \times (2^6) \times (2^6) \times (2^6) \times (2^6) \times (2^6) \times (2^6) = (2^6)^7 = 2^{42}$
### Step 2: Extracting m and n
We need to express this as m^n$m^n$ where m$m$ is the least natural number.
The least base possible is m = 2$m = 2$.
Thus, m = 2$m = 2$ and n = 42$n = 42$.
m + n = 2 + 42 = 44$m + n = 2 + 42 = 44$.
### Pattern Recognition
Permutations into power sets with inclusion constraints always isolate the constrained element and leave the remaining elements free to permute in 2^k-1$2^{k-1}$ subsets.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Maths: Sets
Class 12 Maths: Relations and Functions
Q30jee_main_2024_31_jan_eveningTypes of Relations
Let A = \1, 2, 3, dots dots dots 100\$A = \{1, 2, 3, \dots \dots \dots 100\}$. Let mathbfR$\mathbf{R}$ be a relation on A$A$ defined by (x, y) in mathbfR$(x, y) \in \mathbf{R}$ if and only if 2x = 3y$2x = 3y$. Let mathbfR_1$\mathbf{R}_1$ be a symmetric relation on A$A$ such that mathbfR subset mathbfR_1$\mathbf{R} \subset \mathbf{R}_1$ and the number of elements in mathbfR_1$\mathbf{R}_1$ is n$n$. Then, the minimum value of n$n$ is
Numerical Answer.Answer: 66 to 66
Solution
### Related Formula
textA relation R_1 text is symmetric if (x,y) in R_1 implies (y,x) in R_1$\text{A relation } R_1 \text{ is symmetric if } (x,y) \in R_1 \implies (y,x) \in R_1$
### Core Logic
Given 2x = 3y$2x = 3y$ for (x,y) in A times A$(x,y) \in A \times A$.
Elements in A$A$ range up to 100. Thus y = frac2x3$y = \frac{2x}{3}$. For y$y$ to be an integer, x$x$ must be a multiple of 3.
x in \3, 6, 9, dots, 99\$x \in \{3, 6, 9, \dots, 99\}$ are valid inputs. There are frac993 = 33$\frac{99}{3} = 33$ such elements.
The maximum value of x$x$ is 99$99$, which gives y = frac2(99)3 = 66 le 100$y = \frac{2(99)}{3} = 66 \le 100$ (valid).
The relation R$R$ explicitly contains 33 elements: R = \(3,2), (6,4), dots, (99,66)\$R = \{(3,2), (6,4), \dots, (99,66)\}$.
None of the pairs in R$R$ have x=y$x=y$ because 2x=3x implies x=0$2x=3x \implies x=0$, which is not in A$A$.
For mathbfR_1$\mathbf{R}_1$ to be a symmetric relation containing mathbfR$\mathbf{R}$, it must contain all elements of mathbfR$\mathbf{R}$ and their inverse pairs (y,x)$(y,x)$.
Minimum number of elements in mathbfR_1 = 2 times |mathbfR| = 2 times 33 = 66$\mathbf{R}_1 = 2 \times |\mathbf{R}| = 2 \times 33 = 66$.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 12 Maths: Relations and Functions
Q6jee_main_2024_31_jan_morningComposition of Functions
If f(x) = frac4x + 36x - 4, x neq frac23$f(x) = \frac{4x + 3}{6x - 4}, x \neq \frac{2}{3}$ and (fof)(x) = g(x)$(fof)(x) = g(x)$, where g : mathbbR - left\frac23right\ to mathbbR - left\frac23right\$g : \mathbb{R} - \left\{\frac{2}{3}\right\} \to \mathbb{R} - \left\{\frac{2}{3}\right\}$, then (gogog)(4)$(gogog)(4)$ is equal to
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