If a-b and a+b are twin prime a and b are necessarily

Step-by-step explanation:

Twin primes are defined as two primes which differ by 2.

Examples are (3,5), (5,7), (11,13),(17,19),(41,43),(71,73),(101,103)...

which can be written as

(4-1,4+1), (6-1,6+1), (12-1,12+1),(18-1,18+1),(42-1,42+1),(72-1,72+1),(102-1,102+1)...

from which we can observe that

- "b" must be equal to one to provide a difference of two as required by the definition of twin primes,

- "a" and "b" must be integers, since "b" must be one,

- "a" must be even.  If "a" is odd, then both a-b and a+b will be even, and they cannot be both primes, also

- "a" above 10 cannot end in the digit 4 or 6 else either (a-b) or (a+b) will be a multiple of 5, which is not prime.

If there are other conditions, feel free to add-on.

the function makes a strait line horizontally with no x intercept but a y intercept at 9.