JEE Main · Mathematics ↓ Falling

Sets, Relations and Functions appeared 65 times across 3 years — 7.5% of Mathematics. This question is from Composite Functions.

Year 2026 2025 2024 Total
Questions 19 31 15 65

If f(x)= cases2+2x,& -1≤ x lt 0 1-(x)/(3),& 0≤ x≤ 3 cases; g(x)= cases-x,& -3≤ x≤ 0 x,& 0 lt x≤ 1 cases , then range of (fog(x)) is

Solution & Explanation

Related Formula
f(g(x)) = f(y) where y = g(x)

The domain restrictions of f(y) must be cross-checked against the range evaluated for g(x).

Core Logic

First, analyze the range of the inner function g(x): g(x) = -x for -3 ≤ x ≤ 0. The range here is [0, 3]. g(x) = x for 0 lt x ≤ 1. The range here is (0, 1]. Therefore, the complete range of g(x) across its entire domain [-3, 1] is [0, 3]. Note that g(x) ≥ 0 for all valid x.

Composite Functions
Composite Functions

Now, plug g(x) into f(x):

f(g(x)) = cases2+2g(x),& -1 ≤ g(x) lt 0 (1) 1-(g(x))/(3),& 0 ≤ g(x) ≤ 3 (2) cases

Composite Functions
Composite Functions

Step 1: Evaluate the Branches

Check branch (1): -1 ≤ g(x) lt 0. Since we already established the range of g(x) is entirely non-negative (g(x) ≥ 0), this branch condition is never satisfied. No values of x map here (x in φ).

Check branch (2): 0 ≤ g(x) ≤ 3. This perfectly aligns with the entire range of g(x). Hence, this branch is active for all x in [-3, 1]. We evaluate f(g(x)) = 1 - (g(x))/(3). Since g(x) spans all values continuously from 0 to 3: When g(x) = 0 ⇒ f(g(x)) = 1 - 0 = 1. When g(x) = 3 ⇒ f(g(x)) = 1 - 1 = 0.

Since g(x) is continuous and covers [0, 3], 1 - (g(x))/(3) covers [0, 1] continuously.

Step 2: Final Conclusion

The range of f(g(x)) is purely evaluated from branch (2), leading to [0, 1].

Pattern Recognition

When finding the range of f(g(x)), evaluate the global range of g(x) first. Use that resulting interval as the "domain" input for f(x) to trace the final output bounds, eliminating unneeded piecewise branches.

Chapter Mix

Class 11 Mathematics: Sets, Relations and Functions

Reference Study Guides

More Sets, Relations and Functions Previous-Year Questions — Page 2

Q14 jee_main_2026_22_january_morning Domain of a Function
If the domain of the function f(x) = ⁻¹((5 - x)/(3 + 2x)) + (1)/( (10 - x)) is (- ∞, α] [β, γ) - δ, then 6(α + β + γ + δ) is equal to
  • A. 70
  • B. 66
  • C. 67
  • D. 68

Solution

Related Formula
Domain of ⁻¹(y) is -1 ≤ y ≤ 1 Domain of (1)/( (z)) is z > 0, z ≠ 1
Core Logic

For f(x) to be defined, two main conditions must hold:

  • -1 ≤ (5 - x)/(2x + 3) ≤ 1
  • 10 - x > 0 and 10 - x ≠ 1
Step 1: Solving the Logarithmic Domain

10 - x > 0 x < 10 10 - x ≠ 1 x ≠ 9

Step 2: Solving the Inverse Sine Domain

-1 ≤ (5 - x)/(2x + 3) ≤ 1 This is equivalent to |(5 - x)/(2x + 3)| ≤ 1, which means:

(5 - x)² ≤ (2x + 3)² (assuming x ≠ -1.5) (5 - x)² - (2x + 3)² ≤ 0

Factor as difference of squares:

(5 - x - (2x + 3))(5 - x + 2x + 3) ≤ 0 (2 - 3x)(x + 8) ≤ 0

Multiply by -1 and flip the inequality:

(3x - 2)(x + 8) ≥ 0

So, x in (-∞, -8] [(2)/(3), ∞).

Step 3: Intersection of Domains

Intersecting with x < 10 and x ≠ 9:

Domain = (-∞, -8] [(2)/(3), 10) - 9

Comparing with the given form (-∞, α] [β, γ) - δ, we have: α = -8, β = (2)/(3), γ = 10, δ = 9.

Step 4: Final Value Calculation

Evaluate 6(α + β + γ + δ):

6(-8 + (2)/(3) + 10 + 9) = 6(11 + (2)/(3)) = 6((35)/(3)) = 70
Pattern Recognition

Instead of solving two separate rational inequalities for ≤ 1 and ≥ -1, converting the absolute value fraction into a difference of squares quickly bypasses sign analysis pitfalls, delivering the required critical points effortlessly.

Chapter Mix

Class 11 Maths: Sets, Relations and Functions Class 12 Maths: Inverse Trigonometric Functions

Q3 jee_main_2026_22_january_evening Number of Elements in Relation
The number of elements in the relation R = (x,y) : 4x² + y² < 52, x, y in Z is
  • A. 77
  • B. 89
  • C. 67
  • D. 86

Solution

Related Formula

Count integer pairs (x, y) satisfying 4x² + y² < 52.

Core Logic

Systematically test possible integer values of x:

  • For x = 0: y² < 52 y in 0, ± 1, , ± 7 (15 values)
  • For x = ± 1: y² < 48 y in 0, ± 1, , ± 6 (2 × 13 = 26 values)
  • For x = ± 2: y² < 36 y in 0, ± 1, , ± 5 (2 × 11 = 22 values)
  • For x = ± 3: y² < 16 y in 0, ± 1, ± 2, ± 3 (2 × 7 = 14 values)
Step 1: Total Sum

Total elements = 15 + 26 + 22 + 14 = 77.

Pattern Recognition

Bound x first since its coefficient is larger, then sum valid values of y symmetrically.

Chapter Mix

Class 11 Maths: Sets and Relations

Q14 jee_main_2026_22_january_evening Domain of Composite Function
Let the domain of the function f(x) = ₃ ₅ (7 - ₂ (x² - 10x + 85)) + ⁻¹ (|(3x-7)/(17-x)|) be (α, β]. Then α + β is equal to:
  • A. 10
  • B. 12
  • C. 9
  • D. 8

Solution

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 λ = x² - 10x + 85.

  • Logarithmic conditions:
  • λ > 0
  • 7 - ₂ λ > 0 λ < 2⁷
  • ₅ (7 - ₂ λ) > 0 7 - ₂ λ > 1 ₂ λ < 6 λ < 64
  • Combining: 0 < x² - 10x + 85 < 64 x² - 10x + 21 < 0 x in (3, 7).

Step 1: Inverse Sine Domain
|(3x-7)/(17-x)| ≤ 1 -1 ≤ (3x-7)/(17-x) ≤ 1 x in [-5, 6]
Step 2: Intersection of Domains

Intersection of x in (3, 7) and x in [-5, 6] is (3, 6]. Here α = 3, β = 6 α + β = 9.

Pattern Recognition

Unpack nested logarithms sequentially from outside in to determine tight bounds on inner quadratic.

Chapter Mix

Class 11 Maths: Functions and Graphs

Q18 jee_main_2026_22_january_evening Greatest Integer Function Properties
Let f(x) = [x]² - [x+3] - 3, x in R where [·] is the greatest integer function. Then:
  • A. f(x) > 0 only for x in [4,∞)
  • B. f(x) < 0 only for x in [-1,3)
  • C. ∫₀² f(x) dx = -6
  • D. f(x) = 0 for finitely many values of x.

Solution

Related Formula

Property of greatest integer function: [x+k] = [x] + k for integer k.

Core Logic

Simplify f(x):

f(x) = [x]² - ([x] + 3) - 3 = [x]² - [x] - 6 = ([x] + 2)([x] - 3)
  • f(x) < 0 -2 < [x] < 3 [x] in -1, 0, 1, 2 x in [-1, 3).
Step 1: Check Other Options
  • f(x) > 0 [x] < -2 or [x] > 3 x in (-∞, -2) [4, ∞) (Option 1 incorrect).
  • ∫₀² f(x) dx = ∫₀¹ (-6) dx + ∫₁² (-6) dx = -12 (Option 3 incorrect).
  • f(x) = 0 [x] = 3 or [x] = -2, which has infinitely many solutions (Option 4 incorrect).
Pattern Recognition

Factorize expression in terms of [x] to easily check intervals for positive/negative values.

Chapter Mix

Class 11 Maths: Functions and Graphs

Q6 jee_main_2026_23_january_morning Equivalence Relations
Let A = -2, -1, 0, 1, 2, 3, 4. Let R be a relation on A defined by xRy if and only if 2x + y ≤ 2. Let l be the number of elements in R. Let m and n be the minimum number of elements required to be added in R to make it reflexive and symmetric relations respectively. Then l + m + n is equal to:
  • A. 32
  • B. 34
  • C. 33
  • D. 35

Solution

Related Formula
Reflexive: (a,a) in R a in A Symmetric: (a,b) in R ⇒ (b,a) in R
Core Logic

Evaluate 2x + y ≤ 2 for all elements in A = -2, -1, 0, 1, 2, 3, 4 to find pairs (x,y) in R. For x = -2: y ≤ 6 ⇒ y in -2, -1, 0, 1, 2, 3, 4 (7 pairs) For x = -1: y ≤ 4 ⇒ y in -2, -1, 0, 1, 2, 3, 4 (7 pairs) For x = 0: y ≤ 2 ⇒ y in -2, -1, 0, 1, 2 (5 pairs) For x = 1: y ≤ 0 ⇒ y in -2, -1, 0 (3 pairs) For x = 2: y ≤ -2 ⇒ y in -2 (1 pair) For x = 3: y ≤ -4 ⇒ None For x = 4: y ≤ -6 ⇒ None

Total elements in R, l = 7 + 7 + 5 + 3 + 1 = 23.

Step 1: Calculate Minimum Additions for Reflexivity (m)

For R to be reflexive, we need (x,x) in R for all x in A. Let's check which are missing: 2(x) + x = 3x ≤ 2. This holds for x = -2, -1, 0. It fails for x = 1, 2, 3, 4. Thus, we need to add 4 elements: (1,1), (2,2), (3,3), (4,4). So, m = 4.

Step 2: Calculate Minimum Additions for Symmetry (n)

For R to be symmetric, if (x,y) in R, we must have (y,x) in R. Let's check elements where 2x+y ≤ 2 but 2y+x > 2. We list pairs where (x,y) in R but (y,x) R: For x = -2: ( -2, 3 ) and ( -2, 4 ) are in R. Inverse (3, -2) has 2(3)+(-2) = 4 > 2 (not in R). Add 2 elements. For x = -1: (-1, 2), (-1, 3), (-1, 4) are in R. Inverses: (2, -1) has 2(2)-1=3>2; (3, -1) has 2(3)-1=5>2; (4, -1) has 2(4)-1=7>2. Add 3 elements. For x = 0: (0, 2) is in R. Inverse (2, 0) has 2(2)+0=4>2. Add 1 element. Total pairs to add to make it symmetric, n = 2 + 3 + 1 = 6. (The pairs to add are (3,-2), (4,-2), (2,-1), (3,-1), (4,-1), (2,0)).

Step 3: Final Sum
l + m + n = 23 + 4 + 6 = 33
Pattern Recognition

Counting discrete relations systematically over a small finite set avoids oversight. Breaking it down by individual x constraints builds an exhaustive map.

Chapter Mix

Class 12 Maths: Relations and Functions

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