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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 5

Q53 jee_main_2025_07_april_evening Set Inclusion and Regions
Let A = \(alpha ,beta)in mathbfRtimes mathbfR:|alpha -1|leq 4 text and |beta -5|leq 6\ and B = \(alpha , beta) in mathbfR times mathbfR: 16 (alpha - 2)^2 + 9 (beta - 6)^2 leq 144\. Then
  • A. B subset A
  • B. A cup B = \(x, y) : -4 leq x leq 4, -1 leq y leq 11\
  • C. neither A subset B nor B subset A
  • D. A subset B

Solution

### Related Formula An ellipse equation is structured as: frac(x-h)^2a^2 + frac(y-k)^2b^2 leq 1 ### Core Logic Analyzing set A: |alpha - 1| le 4 implies -4 le alpha - 1 le 4 implies -3 le alpha le 5 |beta - 5| le 6 implies -6 le beta - 5 le 6 implies -1 le beta le 11 Thus, region A forms a rectangle bounded between x in [-3, 5] and y in [-1, 11]. Analyzing set B: 16(alpha - 2)^2 + 9(beta - 6)^2 le 144 Dividing by 144: frac(alpha - 2)^29 + frac(beta - 6)^216 le 1 This represents the interior and boundary of an ellipse centered at (2, 6) with semi-minor axis a = 3 and semi-major axis b = 4. ### Step 1: Spatial Inclusion Check Let's check the extreme horizontal and vertical extents of the ellipse B: Horizontal extent: x in [2 - 3, 2 + 3] = [-1, 5] Vertical extent: y in [6 - 4, 6 + 4] = [2, 10] Comparing with the boundaries of rectangle A (x in [-3, 5] and y in [-1, 11]): [-1, 5] subseteq [-3, 5] [2, 10] subseteq [-1, 11]
Set Inclusion and Regions diagram for Q53 - JEE Main 2025 Evening
Set Inclusion and Regions diagram for Q53 - JEE Main 2025 Evening
Since all points of the ellipse lie perfectly inside the rectangular region, we conclusively find that B subset A. ### Pattern Recognition A bounding box check (finding h pm a and k pm b) for conics is the fastest analytical shortcut to verify set inclusion without plotting extensive coordinates. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Sets, Relations and Functions Class 11 Mathematics: Conic Sections
Q54 jee_main_2025_07_april_evening Range of Rational Functions
If the range of the function f(x) = frac5 - xx^2 - 3x + 2, x neq 1, 2, is (-infty , alpha ] cup [ beta , infty), then alpha^2 +beta^2 is equal to :
  • A. 190
  • B. 192
  • C. 188
  • D. 194

Solution

### Related Formula For a quadratic equation Ax^2 + Bx + C = 0 to yield real roots, its discriminant must satisfy: D = B^2 - 4AC ge 0 ### Core Logic Set y = frac5 - xx^2 - 3x + 2: y(x^2 - 3x + 2) = 5 - x yx^2 - 3xy + 2y + x - 5 = 0 Rearranging into a standard quadratic equation in terms of x: yx^2 + (1 - 3y)x + (2y - 5) = 0 ### Step 1: Discriminant Method Case I: If y = 0, the equation simplifies to x - 5 = 0 implies x = 5, which is a valid part of the domain. Thus, 0 belongs to the range. Case II: If y neq 0, for x to be real, D ge 0: (1 - 3y)^2 - 4(y)(2y - 5) ge 0 9y^2 + 1 - 6y - 8y^2 + 20y ge 0 y^2 + 14y + 1 ge 0 ### Step 2: Solving the Inequality Completing the square for y^2 + 14y + 1 ge 0: (y + 7)^2 - 48 ge 0 implies (y + 7)^2 ge (4sqrt3)^2 This gives: y le -7 - 4sqrt3 quad textor quad y ge -7 + 4sqrt3 Comparing with the interval (-infty , alpha ] cup [ beta , infty): alpha = -7 - 4sqrt3 beta = -7 + 4sqrt3 ### Step 3: Finding alpha^2 + beta^2 Using algebraic identities: alpha^2 + beta^2 = (-7 - 4sqrt3)^2 + (-7 + 4sqrt3)^2 = 2(7^2 + (4sqrt3)^2) = 2(49 + 48) = 2(97) = 194 ### Pattern Recognition For rational expressions of the form fractextLineartextQuadratic, converting to a quadratic in x and forcing D ge 0 establishes the range boundaries elegantly. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Sets, Relations and Functions
Q52 jee_main_2025_24_jan_evening One-One and Onto Functions
The function f:(-infty,infty)rightarrow(-infty,1), defined by f(x)=frac2^x-2^-x2^x+2^-x is: [cite: 3251, 3252]
  • A. textOne-one but not onto
  • B. textOnto but not one-one
  • C. textBoth one-one and onto
  • D. textNeither one-one nor onto

Solution

### Related Formula A function is one-one if its derivative is strictly monotonic (always positive or always negative) across its domain. It is onto if its range equals its co-domain. ### Core Logic Rewrite the function by multiplying the numerator and denominator by 2^x: f(x) = frac2^2x - 12^2x + 1 = 1 - frac22^2x + 1 ### Step 1: Check One-One property Differentiating f(x) with respect to x : f'(x) = frac2(2^2x + 1)^2 cdot 2 cdot 2^2x cdot ln 2 = frac4 cdot 2^2x cdot ln 2(2^2x + 1)^2 Since 2^2x > 0 and ln 2 > 0, f'(x) > 0 always. Thus, f(x) is strictly increasing, confirming it is a one-one function. ### Step 2: Check Onto property Analyze the limits at boundaries [cite: 3880, 3881]: lim_x to -infty f(x) = 1 - frac20 + 1 = -1 lim_x to infty f(x) = 1 - 0 = 1 Thus, the range of the function is (-1, 1). Since the given co-domain is (-infty, 1) and textRange neq textCo-domain , the function is not onto. ### Pattern Recognition The expression given is a shifted form of the hyperbolic tangent function tanh(x ln 2). Hyperbolic tangent always maps to (-1, 1), making its restriction against (-infty, 1) non-surjective (not onto). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Relations and Functions
Q58 jee_main_2025_24_jan_evening Linear Programming and Inequalities in Two Variables
Let the points (frac112,alpha) lie on or inside the \triangle with sides x+y=11, x+2y=16 and 2x+3y=29 Then the product of the smallest and the largest values of a is equal to: [cite: 3284, 3285, 3286, 3287, 3288, 3289]
  • A. 22
  • B. 44
  • C. 33
  • D. 55

Solution

### Related Formula For a vertical line x = x_0 crossing a bounded region, the valid coordinates of y sit between the boundary lines intersecting that specific line vertical plane. ### Core Logic The point given is fixed at x = frac112 = 5.5[cite: 3285, 3925]. We evaluate the values of y along this vertical line segment across each boundary edge.
Linear Programming region graph for Q58 - JEE Main 2025 Evening
Linear Programming region graph for Q58 - JEE Main 2025 Evening
### Step 1: Evaluate Intersections Substitute x = frac112 into the three linear constraints: 1. From x + y = 11: frac112 + y = 11 Rightarrow y = 11 - 5.5 = 5.5 2. From x + 2y = 16: frac112 + 2y = 16 Rightarrow 2y = 16 - 5.5 = 10.5 Rightarrow y = 5.25 3. From 2x + 3y = 29: 2left(frac112right) + 3y = 29 Rightarrow 11 + 3y = 29 Rightarrow 3y = 18 Rightarrow y = 6 ### Step 2: Define Extrema and Multiply Checking the internal region of the \triangle bounded by these lines [cite: 3286, 3287], the valid range for alpha along the section line is delimited by y = 5.5 and y = 6: alpha_min = frac112 = 5.5 alpha_max = 6 The product of the limits is : alpha_min cdot alpha_max = frac112 times 6 = 33 ### Pattern Recognition Instead of drawing full coordinate diagrams or computing all three vertex points, evaluating values directly at the fixed coordinate constraint x = 5.5 saves time during multi-line area problems. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Mathematics: Linear Inequalities Class 11 Mathematics: Straight Lines
Q71 jee_main_2025_24_jan_evening Number of Functions under Constraints
Number of functions f:\1,2,dots,100\rightarrow\0,1\, that assign 1 to exactly one of the positive integers less than or equal to 98, is equal to \_\_\_\_.
Numerical Answer. Answer: 392

Solution

### Related Formula Fundamental Counting Principle: If an operation can be performed in n_1 ways, followed by a second operation in n_2 ways, the total configurations equal n_1 times n_2. ### Core Logic The domain set contains integers from 1 to 100. We divide the mapping requirements across distinct subsets of this domain[cite: 4064, 4068, 4069].
Function mapping grid for Q71 - JEE Main 2025 Evening
Function mapping grid for Q71 - JEE Main 2025 Evening
### Step 1: Choose the single element from \1, 2, dots, 98\ We must assign the image value 1 to exactly one positive integer from the \subset \1, 2, dots, 98\. The number of ways to pick this single element is : binom981 = 98 text ways ### Step 2: Mapping remaining elements The remaining 97 elements in the \1, 2, dots, 98\ \subset cannot map to 1, so they must map to 0. This leaves exactly 1 choice per remaining element. For the final two elements in the domain, 99 and 100, there are no structural constraints [cite: 4068, 4069]: - Element 99 can map to either 0 or 1 (2 options) . - Element 100 can map to either 0 or 1 (2 options). ### Step 3: Total functions combination Multiply the independent choices together : textTotal functions = 98 times 2 times 2 = 392 [cite: 4065, 4067] ### Pattern Recognition Separate domains tightly into restricted blocks vs completely free components. Realizing that elements 99 and 100 behave independently with full co-domain targets leaves a clear product formulation. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 12 Mathematics: Relations and Functions Class 11 Mathematics: Permutations and Combinations

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