Question

Ann thought of a number N, multiplied it by 5 and added 7. Then she told the result R to Jim. Find the domain and the range of this function.?

Answer 1

Domain: `R in NN` (Assumed)
Range: `[12,+oo)`

Explanation:

Let `R =f(N)`

First I will assume that Ann thought of a natural number `N`.

Hence, the domain of `f(N)` is the set of natural numbers.

`:.` Domain of `f(N)`:is `NN`

We are told that `f(N) = 5N+7`

Since `N in NN` the least value of `N` is `1`

`:. f(N)_min = 5xx1+7`

`= 12`

Since `f(N)` has no finite upper bound we are forced to an infinite upper range. Obviously, in 'real life' this makes no sense.

Nevertheless, strictly as this question is posed, the range of `f(N)` is `[12,+oo)`