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If the domain of the function f(x) = log_e left(frac2x + 34x^2 + x - 3right) + cos^-1left(frac2x - 1x + 2right) is (alpha, beta] , then the value of 5beta - 4alpha is equal to

Solution & Explanation

### Related Formula textDomain of log_e(A): A gt 0 textDomain of cos^-1(B): -1 le B le 1 ### Core Logic Condition 1: Logarithm domain frac2x + 34x^2 + x - 3 gt 0 Factorizing the denominator: 4x^2 + 4x - 3x - 3 = 4x(x+1) - 3(x+1) = (4x-3)(x+1). frac2x + 3(4x - 3)(x + 1) gt 0 Critical points are x = -frac32, -1, frac34. Using the wavy curve method: The intervals where it is positive are left(-frac32, -1right) cup left(frac34, inftyright). Let this be set D_1. ### Step 1: Inverse Trigonometric Domain Condition 2: Arc cosine domain -1 le frac2x - 1x + 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 Critical points are x = -2, -frac13. The valid set is (-infty, -2) cup left[-frac13, inftyright). (ii) frac2x - 1x + 2 le 1 Rightarrow frac2x - 1x + 2 - 1 le 0 Rightarrow fracx - 3x + 2 le 0 Critical points are x = -2, 3. The valid set is (-2, 3]. Intersection for the cosine domain (D_2): (-2, 3] cap left( (-infty, -2) cup left[-frac13, inftyright) right) = left[-frac13, 3right]. ### Step 2: Finding Total Domain Total domain D = D_1 cap D_2: D = left( left(-frac32, -1right) cup left(frac34, inftyright) right) cap left[-frac13, 3right] Since left[-frac13, 3right] starts strictly greater than -1, the overlap with left(-frac32, -1right) is empty. Overlap with left(frac34, inftyright) occurs from frac34 to 3. Thus, D = left(frac34, 3right]. ### Step 3: Calculating Final Expression Comparing with (alpha, beta]: alpha = frac34 and beta = 3. We need to find 5beta - 4alpha: 5(3) - 4left(frac34right) = 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 missing the cosine bound) prunes manual checking. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Functions

Reference Study Guides

More Functions Previous-Year Questions — Page 9

Q12 jee_main_2024_30_jan_morning Domain and Range
If the domain of the function f(x) = cos^-1left(frac2 - |x|4right) + (log_e (3 - x))^-1 is [-alpha, beta) - \gamma\, then alpha + beta + gamma is equal to:
  • A. 12
  • B. 9
  • C. 11
  • D. 8

Solution

### Related Formula -1 leq textargument of cos^-1 leq 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 ### Core Logic For f(x) to be defined, both terms must be defined independently. Term 1: cos^-1left(frac2 - |x|4right) The domain requires: -1 leq frac2 - |x|4 leq 1 -4 leq 2 - |x| leq 4 -6 leq -|x| leq 2 -2 leq |x| leq 6 Since |x| is always non-negative, the valid condition reduces to |x| leq 6. This implies x in [-6, 6] quad dots (1) ### Step 1: Domain of logarithmic term Term 2: (log_e(3 - x))^-1 = frac1log_e(3 - x) The argument of the logarithm must be positive: 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) ### 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, 3) - \2\ Comparing this with the given domain [-alpha, beta) - \gamma\: alpha = 6, beta = 3, gamma = 2. ### Step 3: Calculating target value 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
Q21 jee_main_2024_30_jan_morning Set 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) ### Core Logic
Set Operations diagram for Q21 - JEE Main 2024 Morning
Set Operations diagram for Q21 - JEE Main 2024 Morning
Let x be the number of students who passed in all three subjects, so n(M cap P cap C) = x. We are given: n(M) = 20, n(P) = 25, n(C) = 16 n(M cup P cup C) = 40 Constraints: n(M cap P) le 11 n(P cap C) le 15 n(M cap C) le 15 If we let n(M cap P) = 11, then the region representing only M cap P is 11 - x. For this to be non-negative, x le 11. ### Step 1: Testing x = 11
Set Operations diagram for Q21 - JEE Main 2024 Morning
Set Operations diagram for Q21 - JEE Main 2024 Morning
Assume x = 11. To maximize, let's fix n(M cap P) = 11. This leaves 0 students in (M cap P) - (M cap P cap C). Let n(M cap C) = 11 + z and n(P cap C) = 11 + y. Constraints limit these subsets: 11 + z le 15 Rightarrow z le 4 11 + y le 15 Rightarrow y le 4 Filling the Venn diagram nodes: Only M = 20 - 11 - z - 0 = 9 - z Only P = 25 - 11 - y - 0 = 14 - y Only 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 39 - y - z = 40 Rightarrow y + z = -1 Since subsets cannot be negative, x=11 is impossible. ### Step 2: Testing x = 10
Set Operations diagram for Q21 - JEE Main 2024 Morning
Set Operations diagram for Q21 - JEE Main 2024 Morning
Assume x = 10. Let's construct a valid distribution with x = 10. We can choose intersection values: n(M cap P) = 10, so only M cap P is 0. n(M cap C) = 11, so only M cap C is 1. n(P cap C) = 10, so only P cap C is 0. This gives: Only M = 20 - 10 - 0 - 1 = 9 Only P = 25 - 10 - 0 - 0 = 15 Only C = 16 - 10 - 1 - 0 = 5 Summing up = 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
Q24 jee_main_2024_30_jan_morning Types of Functions
Let A = \1, 2, 3, dots, 7\ and let P(A) denote the power set of A. If the number of functions f: A to P(A) such that a in f(a) forall a in A is m^n, m and n in mathbbN and m is least, then m + n is equal to
Numerical Answer. Answer: 44 to 44

Solution

### Related Formula textSize of Power Set |P(A)| = 2^|A| ### Core Logic For a function f: A to P(A), each element a in A maps to a subset of A. The condition is a in f(a). This means that the subset assigned to a must contain the element a. How many such subsets exist in P(A)? Since |A| = 7, there are 2^7 total subsets. Exactly half of these contain a specific element a. Number of subsets containing 'a' is 2^7-1 = 2^6 = 64. ### Step 1: Calculating total functions For each element in A (which has 7 elements), there are independently 2^6 choices for its image in P(A). Total options for 1 will be 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 ### Step 2: Extracting m and n We need to express this as m^n where m is the least natural number. The least base possible is m = 2. Thus, m = 2 and n = 42. 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 subsets. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Sets Class 12 Maths: Relations and Functions
Q30 jee_main_2024_31_jan_evening Types of Relations
Let A = \1, 2, 3, dots dots dots 100\. Let mathbfR be a relation on A defined by (x, y) in mathbfR if and only if 2x = 3y. Let mathbfR_1 be a symmetric relation on A such that mathbfR subset mathbfR_1 and the number of elements in mathbfR_1 is n. Then, the minimum value of 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 ### Core Logic Given 2x = 3y for (x,y) in A times A. Elements in A range up to 100. Thus y = frac2x3. For y to be an integer, x must be a multiple of 3. x in \3, 6, 9, dots, 99\ are valid inputs. There are frac993 = 33 such elements. The maximum value of x is 99, which gives y = frac2(99)3 = 66 le 100 (valid). The relation R explicitly contains 33 elements: R = \(3,2), (6,4), dots, (99,66)\. None of the pairs in R have x=y because 2x=3x implies x=0, which is not in A. For mathbfR_1 to be a symmetric relation containing mathbfR, it must contain all elements of mathbfR and their inverse pairs (y,x). Minimum number of elements in mathbfR_1 = 2 times |mathbfR| = 2 times 33 = 66. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Relations and Functions
Q6 jee_main_2024_31_jan_morning Composition of Functions
If f(x) = frac4x + 36x - 4, x neq frac23 and (fof)(x) = g(x), where g : mathbbR - left\frac23right\ to mathbbR - left\frac23right\, then (gogog)(4) is equal to
  • A. -frac1920
  • B. frac1920
  • C. -4
  • D. 4

Solution

### Core Logic f(x) = frac4x + 36x - 4 Compute g(x) = f(f(x)): g(x) = frac4left(frac4x + 36x - 4right) + 36left(frac4x + 36x - 4right) - 4 = frac16x + 12 + 18x - 1224x + 18 - 24x + 16 = frac34x34 = x ### Step 1: Composition Evaluation Since g(x) = x, g is the identity function. (gogog)(4) = g(g(g(4))) = 4 ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Relations and Functions

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