✓ Board-verified
Mathematics · 2026 · 1 mark
CBSE 2026 · Region 4 · Set 1 · Q20
Assertion (A): A function f: N → N given by f ( x )= x^3+2, ∀ x ∈ N is one-one but not onto. Reason (R): Since ∀ y ∈ N (Codomain), there does not…
Assertion (A): A function $\displaystyle \mathrm{f}: \mathrm{N} \rightarrow \mathrm{N}$ given by $\displaystyle \mathrm{f}(\mathrm{x})=\mathrm{x}^{3}+2, \forall \mathrm{x} \in \mathrm{N}$ is one-one but not onto.
Reason (R) : Since $\displaystyle \forall \mathrm{y} \in \mathrm{N}$ (Codomain), there does not exist $\displaystyle \mathrm{x}=(\mathrm{y}-2)^{1 / 3}$ in N (Domain) such that $\displaystyle \mathrm{f}(\mathrm{x})=\mathrm{x}^{3}+2=\mathrm{y}$.
Official answer
(A)
Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
All Relations and Functions questions2026 question paperNCERT solutions: Relations and FunctionsPractice Relations and Functions →
More from Relations and Functions
- A function f: R_+ → R (where R_+ is the set of all non-negative real numbers) defined by f(x)=4 x+3 is:2024
- Let f: A → B be defined by f(x)=(x-2)/(x-3), where A=R-{3} and B=R-{1}. Discuss the bijectivity of the function.2025
- If f(x)=|x|+|x-1|, then which of the following is correct?2025
- A class-room teacher is keen to assess the learning of her students the concept of "relations" taught to them. She writes the following five…2025
- If f: N → W is defined as f(n)= {n/2, if n is even; 0, if n is odd}, then f is:2025
- A function f:[-4,4] →[0,4] is given by f(x)=√(16-x^2). Show that f is an onto function but not a one-one function. Further, find all possible values…2023
- If f(x)=-2 x^8, then the correct statement is:2025
- Prove that a function f:[0, ∞) →[-5, ∞) defined as f(x)=4 x^2+4 x-5 is both one-one and onto.2023
CBSE Class 12 Mathematics past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.