# Class 12 Mathematics Relations and Functions: NCERT Solutions for Question 7

This page focuses on the detailed Relations and Functions question answers for Class 12 Mathematics Relations and Functions, addressing the question: 'In each of the following cases, state whether the function is one-one, onto or bijective. Justify your answer. (i) f : R → R defined by f(x) = 3 – 4x (ii) f : R → R defined by f(x) = 1 + x2 '. The solution provides a thorough breakdown of the question, highlighting key concepts and approaches to arrive at the correct answer. This easy-to-understand explanation will help students develop better problem-solving skills, reinforcing their understanding of the chapter and aiding in exam preparation.
Question 7

## In each of the following cases, state whether the function is one-one, onto or bijective. Justify your answer.(i) f : R → R defined by f(x) = 3 – 4x(ii) f : R → R defined by f(x) = 1 + x2

(i) f: R → R is defined as f(x) = 3 - 4x.

.

∴ f is one-one.

For any real number (y) in R, there existsin R such that

f is onto.

Hence, f is bijective.

(ii) f: R → R is defined as

.

.

does not imply that x1 = x2

For instance,

∴ f is not one-one.

Consider an element - 2 in co-domain R.

It is seen thatis positive for all x ∈ R.

Thus, there does not exist any x in domain R such that f(x) = - 2.

∴ f is not onto.

Hence, f is neither one-one nor onto.