Find the number of positive three-digit integers whose digits are among 9, 8, 7, 5, 3, 1 in which none of the digits are the same.
15
120
216

120

Step-by-step explanation:

The given digits : 9, 8, 7, 5, 3, 1

Number of digits : 6

If repetition of digit is not allowed then we use permutations.

We know that the number of permutations of n things taking r at a time is given by :-

Now, the number of permutations of 6 digits taking 3 at a time is given by :-

step-by-step explanation:

(1, –1), (16, –4), (36, –6)

step-by-step explanation:

given that the function is

this can also be written as

we have to graph this function and check which list of points lie on the graph

see attachment for graph:

we find that the points lying are (1,-1) (16,-4) and (36,-6)

since square root is there we find that x can only be posiitve but y can be since square root both positive and negative.