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Need solution for RD Sharma maths class 12 chapter Functions exercise 2.1 question 5 sub question (i)

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One-one but not onto.


            f:N \rightarrow N given byf(x)=x^2 .


One-one function means every element in the domain has a distinct image in the  co-domain.

Onto function means every element in the co-domain has at least one  pre image in the domain of function.

For any function to be a bijective, the given function be one-one and onto.


Let's start with the injection test.

Let x and y be any two elements in the domain(N) such thatf(x)=f(y)

       \begin{aligned} &f(x)=x^{2}, f(y)=y^{2} \\ &f(x)=f(y) \\ &x^{2}=y^{2} \\ &x=y \end{aligned}

Where x and y are in N , so we don’t get 1 value.

So,f is an injection.

Surjection test:

Let y be any element in the codomain (N) , such thatf(x)=y  for some element x in N .



x=\pm \sqrt{y} which may not be in N


If   y=2, x=\pm \sqrt{2} which is not in N .

So,f is not a surjection.

The condition of bijection is as we know the function should be one-one and onto.

Hence for this, f is not bijection.


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