For what value of [tex]\( c \)[/tex] is the function one-to-one?

[tex]\[
\{(1,2), (2,3), (3,5), (4,7), (5,11), (6, c)\}
\][/tex]

A. 2

B. 5

C. 11

D. 13



Answer :

To determine the correct value of [tex]\( c \)[/tex] such that the function is one-to-one, we need to ensure that each [tex]\( x \)[/tex]-value maps to a unique [tex]\( y \)[/tex]-value.

One way to approach this problem is to observe the sequence of [tex]\( y \)[/tex]-values given by the function and identify any pattern. The given pairs are:
[tex]\[ (1, 2), (2, 3), (3, 5), (4, 7), (5, 11) \][/tex]

First, let's determine if there is a discernible pattern in the [tex]\( y \)[/tex]-values:

- For [tex]\( x = 1 \)[/tex], [tex]\( y = 2 \)[/tex]
- For [tex]\( x = 2 \)[/tex], [tex]\( y = 3 \)[/tex]
- For [tex]\( x = 3 \)[/tex], [tex]\( y = 5 \)[/tex]
- For [tex]\( x = 4 \)[/tex], [tex]\( y = 7 \)[/tex]
- For [tex]\( x = 5 \)[/tex], [tex]\( y = 11 \)[/tex]

Next, we compute the differences between consecutive [tex]\( y \)[/tex]-values:
[tex]\[ \begin{align*} 3 - 2 & = 1, \\ 5 - 3 & = 2, \\ 7 - 5 & = 2, \\ 11 - 7 & = 4. \end{align*} \][/tex]

These differences do not follow a simple arithmetic progression. Instead, they suggest a pattern related to increments associated with prime numbers.

The provided sequence of [tex]\( y \)[/tex]-values appears to increase by the pattern of examining consecutive prime number differences. Specifically, let's test if the differences match the gaps between consecutive primes:

- [tex]\( 2 \to 3 \)[/tex] is the next prime after 2 (difference = 1)
- [tex]\( 3 \to 5 \)[/tex] (difference = 2)
- [tex]\( 5 \to 7 \)[/tex] (difference = 2)
- [tex]\( 7 \to 11 \)[/tex] (difference = 4)

The next prime after 11 is 13 which follows the pattern of prime numbers:

- The difference from 11 to 13 is [tex]\( 2 \)[/tex].

So, we retain the prime number sequence logic. The next number in this pattern after 11 is indeed 13.

Therefore, to maintain the one-to-one nature of the function, the value of [tex]\( c \)[/tex] should be:
[tex]\[ \boxed{13} \][/tex]