Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 202227 JulyMorning Shift
Exam
JEE Main
Year
2022
Date
27 July
Shift
Morning Shift
Subject
Mathematics
Chapter
Functions

JEE Main 2022 · 27 July · Morning Shift · Mathematics · Functions

Let f, g: ℕ - \ 1\ → ℕ be functions defined by f(a) = α , where α...

Let f,g:N−{1}→Nf, g: \mathbb{N} - \left\{1\right\} \to \mathbb{N} be functions defined by f(a)=αf\left(a\right) = \alpha, where α\alpha is the maximum of the powers of those primes pp such that pα{p}^{\alpha} divides aa, and g(a)=a+1g\left(a\right) = a + 1, for all a∈N−{1}a \in \mathbb{N} - \left\{1\right\}. Then, the function f+gf + g is

Options

  1. Aone-one but not onto
  2. Bonto but not one-one
  3. Cboth one-one and onto
  4. Dneither one-one nor onto

Correct answer

D. neither one-one nor onto

Step-by-step solution

Given,

f,g:N−{1}→Nf, g: N - \left\{1\right\} \to N defined as

f(a)=αf\left(a\right) = \alpha, where α\alpha is the maximum power of those primes pp such that pα{p}^{\alpha} divides a.

g(a)=a+1g\left(a\right) = a + 1

Now, f(2)=1,g(2)=3⇒(f+g)(2)=4f\left(2\right) = 1, g\left(2\right) = 3 ⇒ \left(f + g\right)\left(2\right) = 4

f(3)=1,g(3)=4⇒(f+g)(3)=5f\left(3\right) = 1, g\left(3\right) = 4 ⇒ \left(f + g\right)\left(3\right) = 5

f(4)=2,g(4)=5⇒(f+g)(4)=7f\left(4\right) = 2, g\left(4\right) = 5 ⇒ \left(f + g\right)\left(4\right) = 7

f(5)=1,g(5)=6⇒(f+g)(5)=7f\left(5\right) = 1, g\left(5\right) = 6 ⇒ \left(f + g\right)\left(5\right) = 7

We can see \left(f + g\right)\left(5\right) = \left(f + g\right)\left(4\right),so, sof + gisnotone−onefunction</p><p>Now,againwecanseeis not one-one function</p><p>Now, again we can see{f}_\min = 1, {g}_\min = 3</p><p>So,theredoesnotexistany</p><p>So, there does not exist anyx \in N - \left\{1\right\} such that \left(f + g\right)\left(x\right) = 1, 2, 3</p><p></p><p>∴ f + g is not onto

So function is neither one-one nor onto.

Practice Functions on Quantrex Academy →

More from Functions

Let ℕ denote the set of all positive integers. Consider the sets A = \ 1, 2, 3, 4, 5\ and… JEE Advanced 2026Let f:(1,∞)→ℝ be a function defined as f(x) = (x-1)/(x+1) . Let f^ i+1 (x) = f(f^i(x))… JEE Main 2026Let f be a polynomial function such that _2(f(x)) = ( _2(2+(2)/(3)+(2)/(9)+…∞))·… JEE Main 2026Let f: ℝ arrow ℝ be defined as f(x) = (2x^2 - 3x + 2)/(3x^2 + x + 3) . Then f is : JEE Main 2026Let e be the base of natural logarithm and let f: \ 1, 2, 3, 4\ arrow \ 1, e, e^2, e^3\… JEE Main 2026Let f: R arrow R be a function such that f(x) + 3f((π)/(2) - x) = x , x ∈ R . Let the… JEE Main 2026The sum of all the integral values of p such that the equation 3 ^2 x + 12 x - 3 = p , x… JEE Main 2026Let A = \ 1, 2, 3, 4, 5, 6\ . The number of one-one functions f: A arrow A such that f(1)… JEE Main 2026For the function f:[1,∞) arrow [1,∞) defined by f(x)=(x-1)^4+1 , among the two… JEE Main 2026Let for some α ∈ ℝ , f:ℝarrowℝ be a function satisfying f(x+y)=f(x)+2y^2+y+α xy for all… JEE Main 2026Let [·] denote the greatest integer function. If the domain of the function f(x) = ^ -1… JEE Main 2026The number of functions f: \ 1, 2, 3, 4\ arrow \ a, b, c\ , which are not onto, is: JEE Main 2026If the domain of the function f(x) = _ (0.6) (|(2x-5)/(x^2-4)|) is (-∞, a] \ b\ [c, d)… JEE Main 2026Given below are two statements: Statement I: The function f: R arrow R defined by… JEE Main 2026The sum of all the elements in the range of f(x)=Sgn( x)+Sgn( x)+Sgn( x)+Sgn( x) , x ≠ n… JEE Main 2026If g(x)=3 x^ 2 +2 x-3, f(0)=-3 and 4 g(f(x))=3 x^ 2 -32 x+72 , then f(g(2)) is equal to: JEE Main 2026 Full Functions list Functions JEE Maths PYQsJEE Mathematics PYQs All JEE Main PYQs