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Question: Answered & Verified by Expert
A function $\mathrm{f}$ from the set of natural numbers to integers defined by $\mathrm{f}(\mathrm{n})=\left\{\begin{array}{l}\frac{\mathrm{n}-1}{2} \text {, when } n \text { isodd } \\ \frac{\mathrm{n}}{2} \text {, when } \mathrm{n} \text { is even }\end{array}\right.$ is
MathematicsFunctionsJEE MainJEE Main 2003
Options:
  • A
    neither one-one nor onto
  • B
    one-one but not onto
  • C
    onto but not one-one
  • D
    one-one and onto both.
Solution:
2857 Upvotes Verified Answer
The correct answer is:
one-one and onto both.
$f: N \rightarrow 1$
$f(1)=0, f(2)=-1, f(3)=-1, f(4)=-2$
$f(5)=2$, and $f(6)=-3$ so on.


In this type of function every element of set $\mathrm{A}$ has unique image in set $\mathrm{B}$ and there is no element left in set $\mathrm{B}$. Hence $\mathrm{f}$ is one-one and onto function.

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