Let the domain of the function f(x) = log_3 log_5 (7 - log_2 (x^2 - 10x + 85)) + sin^-1 left(left|frac3x-717-xright|right) be (alpha, beta]. Then alpha + beta is equal to:

Solution & Explanation

### Related Formula For logarithmic domain: argument must be strictly positive. For inverse sine domain: argument must lie in [-1, 1]. ### Core Logic
Domain interval intersection for Q14 - JEE Main 2026 Evening
Domain interval intersection for Q14 - JEE Main 2026 Evening
Let lambda = x^2 - 10x + 85. 1. Logarithmic conditions: - lambda > 0 - 7 - log_2 lambda > 0 implies lambda < 2^7 - log_5 (7 - log_2 lambda) > 0 implies 7 - log_2 lambda > 1 implies log_2 lambda < 6 implies lambda < 64 Combining: 0 < x^2 - 10x + 85 < 64 implies x^2 - 10x + 21 < 0 implies x in (3, 7). ### Step 1: Inverse Sine Domain left|frac3x-717-xright| le 1 implies -1 le frac3x-717-x le 1 implies x in [-5, 6] ### Step 2: Intersection of Domains Intersection of x in (3, 7) and x in [-5, 6] is (3, 6]. Here alpha = 3, beta = 6 implies alpha + beta = 9. ### Pattern Recognition Unpack nested logarithms sequentially from outside in to determine tight bounds on inner quadratic. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Functions and Graphs

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Q1 jee_main_2026_21_jan_morning Domain and Range of Inverse Trigonometric Functions
If the domain of the function f(x) = cos^-1left(frac2x - 511 - 3xright) + sin^-1(2x^2 - 3x + 1) is the interval [alpha, beta] , then alpha + 2beta is equal to :
  • A. 1
  • B. 3
  • C. 5
  • D. 2

Solution

### Related Formula For inverse trigonometric functions sin^-1(g(x)) and cos^-1(h(x)), the arguments must satisfy: -1 leq g(x) leq 1 -1 leq h(x) leq 1 ### Core Logic Given f(x) = cos^-1left(frac2x - 511 - 3xright) + sin^-1(2x^2 - 3x + 1) We establish two simultaneous inequalities for the domain: 1) -1 leq frac2x - 511 - 3x leq 1 2) -1 leq 2x^2 - 3x + 1 leq 1 ### Step 1: Solve the Quadratic Inequality From -1 leq 2x^2 - 3x + 1 leq 1: Split into two parts: 2x^2 - 3x + 2 geq 0 (This is always true as discriminant D < 0, a > 0) 2x^2 - 3x leq 0 Rightarrow x(2x - 3) leq 0 x in left[0, frac32right] dots(i) ### Step 2: Solve the Rational Inequality From -1 leq frac2x - 511 - 3x leq 1: Part A: frac2x - 511 - 3x + 1 geq 0 Rightarrow frac2x - 5 + 11 - 3x11 - 3x geq 0 Rightarrow frac6 - x11 - 3x geq 0
Domain interval number line diagram for Q1 - JEE Main 2026 Morning
Domain interval number line diagram for Q1 - JEE Main 2026 Morning
x in left(-infty, frac113right) cup [6, infty) Part B: frac2x - 511 - 3x - 1 leq 0 Rightarrow frac5x - 1611 - 3x leq 0 Rightarrow x in left(-infty, frac165right] cup left(frac113, inftyright) Intersection of Part A and Part B: x in left(-infty, frac165right] cup [6, infty) dots(ii) ### Step 3: Final Intersection Taking the intersection of (i) and (ii): x in left[0, frac32right] Comparing this with [\alpha, \beta], we have \alpha = 0, \beta = \frac{3}{2}. Therefore, \alpha + 2\beta = 0 + 2\left(\frac{3}{2}\right) = 3 ### Pattern Recognition Whenever dealing with dual inverse trig terms, strictly isolate the bounding intervals [-1, 1]$ for each argument separately and use a number line intersection to find the strictest common region. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Functions Class 11 Maths: Linear Inequalities
Q3 jee_main_2026_21_jan_morning Number of Reflexive and Symmetric Relations
The number of relations, defined on the set \a, b, c, d\ , which are both reflexive and symmetric, is equal to:
  • A. 256
  • B. 16
  • C. 1024
  • D. 64

Solution

### Related Formula For a set with n elements, the number of relations that are both reflexive and symmetric is given by: 2^fracn(n-1)2 ### Core Logic A reflexive relation must contain all diagonal pairs (x,x). There is only 1 way to assign these elements (they MUST be present). A symmetric relation requires that if (x,y) is present, (y,x) must also be present. Thus, we only have the freedom to choose whether to include the unordered pairs \x, y\ where x neq y. ### Step 1: Calculate the available independent pairs Number of distinct elements n = 4. Total number of pairs in the cartesian product is n^2 = 16. Number of diagonal pairs (reflexive necessity) = n = 4. Remaining non-diagonal pairs = 16 - 4 = 12. Since symmetry pairs them up (a,b) leftrightarrow (b,a), there are exactly frac122 = 6 independent choices. ### Step 2: Calculate total relations Each of the 6 independent pairs can either be included or excluded (2 choices). Total relations = 1^4 times 2^6 = 64. ### Pattern Recognition Memorize the combinatorics of binary relations for n elements: Total = 2^n^2, Reflexive = 2^n(n-1), Symmetric = 2^n(n+1)/2, Reflexive & Symmetric = 2^n(n-1)/2. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Maths: Sets and Relations
Q13 jee_main_2026_21_jan_evening Operations on Sets
Let A = \x : |x^2 - 10| leq 6\ and B = \x : |x - 2| > 1\. Then
  • A. A cup B = (-infty, 1] cup (2, infty)
  • B. A - B = [2, 3)
  • C. A cap B = [-4, -2] cup [3, 4]
  • D. B - A = (-infty, -4) cup (-2, 1) cup (4, infty)

Solution

### Related Formula |X| leq a iff -a leq X leq a |X| > a iff X < -a text or X > a ### Core Logic Expand both set definitions onto the real number line to find explicit intervals for A and B, then apply set operations to verify the options. ### Step 1: Simplify Set A |x^2 - 10| leq 6 -6 leq x^2 - 10 leq 6 4 leq x^2 leq 16 This yields x in [-4, -2] cup [2, 4]. So, A = [-4, -2] cup [2, 4]. ### Step 2: Simplify Set B |x - 2| > 1 x - 2 < -1 text or x - 2 > 1 x < 1 text or x > 3 So, B = (-infty, 1) cup (3, infty). ### Step 3: Evaluate Options A cup B = (-infty, 1) cup [2, infty) (Option 1 is wrong, has 1]) A cap B = [-4, -2] cup (3, 4] (Option 3 is wrong, has [3,4]) A - B = A cap B^c. B^c = [1, 3]. A cap [1, 3] = [2, 3]. (Option 2 is wrong, has [2, 3)) B - A = B cap A^c. A^c = (-infty, -4) cup (-2, 2) cup (4, infty). B cap A^c = (-infty, -4) cup (-2, 1) cup (4, infty). This matches Option 4 perfectly. ### Pattern Recognition Draw inequalities involving absolute values directly onto a single number line graph to perform union and intersection operations without logic gaps. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Sets and Relations
Q17 jee_main_2026_21_jan_evening Types of Relations
Let A = \2, 3, 5, 7, 9\. Let R be the relation on A defined by xRy if and only if 2x leq 3y. Let ell be the number of elements in R, and m be the minimum number of elements required to be added in R to make it a symmetric relation. Then ell + m is equal to:
  • A. 23
  • B. 25
  • C. 21
  • D. 27

Solution

### Related Formula textA relation R text is symmetric if (x,y) in R implies (y,x) in R. ### Core Logic Check condition y geq frac2x3 for each x in A = \2, 3, 5, 7, 9\ to generate ordered pairs (x,y). Count the pairs to get ell. Then find asymmetric pairs to get m. ### Step 1: Enumerate elements of R x = 2 implies y geq 4/3 = 1.33 implies y in \2, 3, 5, 7, 9\ (5 elements) x = 3 implies y geq 6/3 = 2 implies y in \2, 3, 5, 7, 9\ (5 elements) x = 5 implies y geq 10/3 = 3.33 implies y in \5, 7, 9\ (3 elements) x = 7 implies y geq 14/3 = 4.66 implies y in \5, 7, 9\ (3 elements) x = 9 implies y geq 18/3 = 6 implies y in \7, 9\ (2 elements) Total elements in R is ell = 5 + 5 + 3 + 3 + 2 = 18. ### Step 2: Determine Missing Symmetric Pairs We need to check which reverse pairs (y,x) are missing. (2, 5) in R, but (5, 2) notin R. (2, 7) in R, but (7, 2) notin R. (2, 9) in R, but (9, 2) notin R. (3, 5) in R, but (5, 3) notin R. (3, 7) in R, but (7, 3) notin R. (3, 9) in R, but (9, 3) notin R. (5, 9) in R, but (9, 5) notin R. These are m = 7 pairs that need to be added. Thus, ell + m = 18 + 7 = 25. ### Pattern Recognition When counting pairs for small sets, list them manually by rows. To make symmetric, any non-diagonal pair (x,y) that is present while (y,x) is absent counts as 1 missing element. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Sets and Relations
Q2 jee_main_2026_22_january_morning Symmetric Relation
Let the relation R on the set M = \1, 2, 3, ldots, 16\ be given by R = \(x, y) : 4y = 5x - 3, x, y in M\. Then the minimum number of elements required to be added in R, in order to make the relation symmetric, is equal to
  • A. 1
  • B. 2
  • C. 4
  • D. 3

Solution

### Related Formula textA relation R text is symmetric if (a,b) in R implies (b,a) in R ### Core Logic Given 4y = 5x - 3 implies y = frac5x - 34. We evaluate this for x in \1, 2, ldots, 16\ such that y is also an integer in the same set. - If x = 3 implies y = frac15 - 34 = 3 implies (3,3) in R - If x = 7 implies y = frac35 - 34 = 8 implies (7,8) in R - If x = 11 implies y = frac55 - 34 = 13 implies (11,13) in R - If x = 15 implies y = frac75 - 34 = 18 notin M Therefore, R = \(3,3), (7,8), (11,13)\ ### Step 1: Identifying Missing Symmetric Elements To make the relation symmetric, for every (x,y) in R, the pair (y,x) must also belong to R. - (3,3) is symmetric to itself. - For (7,8), we must add (8,7). - For (11,13), we must add (13,11). Thus, the required elements to be added are (8,7) and (13,11), which totals 2 elements. ### Pattern Recognition When evaluating linear Diophantine equations over a small finite set, simply substitute modular values (here, 5x - 3 equiv 0 pmod 4) to find the explicit ordered pairs, then mechanically apply the equivalence property criteria. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Maths: Sets, Relations and Functions

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