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Question -

Find the domain and range of the following real function:
(i) f(x) = –|x| (ii) f(x) = √(9 – x2



Answer -

(i) Given,

f(x) = –|x|, x  R

We know that,

As f(x)is defined for x  R, the domain of f is R.

It is also seen thatthe range of f(x) = –|x| is all real numbers exceptpositive real numbers.

Therefore, the rangeof f is given by (–∞, 0].

(ii) f(x) = √(9 –x2)

As √(9 – x2) isdefined for all real numbers that are greater than or equal to –3 and less thanor equal to 3, for 9 – x2 ≥ 0.

So, the domainof f(x) is {x: –3 ≤ x ≤ 3} or [–3,3].

Now,

For any value of x inthe range [–3, 3], the value of f(x) will lie between 0 and3.

Therefore, the rangeof f(x) is {x: 0 ≤ x ≤ 3} or [0, 3].

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