CBSE Class 12 Mathematics Relations and Functions Q #2121
COMPETENCY BASED
APPLY
2 Marks Generic-Curriculum VSA
Let $X = \{-1, 0, 1\}, Y = \{0, 2\}$ and a function $f: X \to Y$ defined by $y = 2x^4$, then check whether $f$ is one-one or onto.

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Detailed Solution

Step 1: Evaluate the function for each element in the domain

Given $X = \{-1, 0, 1\}$ and $f(x) = 2x^4$. We calculate the image of each element:

For $x = -1$: $f(-1) = 2(-1)^4 = 2(1) = 2$

For $x = 0$: $f(0) = 2(0)^4 = 2(0) = 0$

For $x = 1$: $f(1) = 2(1)^4 = 2(1) = 2$

Step 2: Check for One-One (Injective) property

A function is one-one if distinct elements have distinct images. Here, $f(-1) = 2$ and $f(1) = 2$. Since two distinct elements in the domain map to the same element in the codomain, the function is not one-one.

Step 3: Check for Onto (Surjective) property

A function is onto if the range equals the codomain. The range of $f$ is $\{0, 2\}$. The codomain $Y$ is given as $\{0, 2\}$. Since Range = Codomain, every element in $Y$ has a pre-image in $X$. Therefore, the function is onto.

Final Answer: The function is not one-one but it is onto.

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must apply the definitions of injective and surjective functions to a specific set-based mapping.
Knowledge Dimension: PROCEDURAL
Justification: The student follows a step-by-step algorithmic process to map elements and verify set equality.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. It tests the foundational understanding of Relations and Functions (Chapter 1) beyond rote memorization.