If x is a positive integer, is x! + (x + 1) a prime number?

[payal919]

This problem is from CAT 1

Q: If x is a positive integer, is x! + (x + 1) a prime number?
(1) x < 10

(2) x is even

Answer is E.

I was able to follow the DS steps and eliminate AD, & B.
I started my calculation for x! + (x+1) using the x = 2, 4, & 8

x = 2: 2! + (2 + 1) = 5, which is prime.
x = 4: 4! + (4+1) = 29, which is prime
x = 8: 8! + (8 + 1) = (8 × 7 × 6 × 5 × 4 × 3 × 2 × 1) + 9.
This expression must be divisible by 3, since both of its terms are divisible by 3. Therefore, it is not a prime number.


I don't understand the explanation provided by the MGMAT for x=8
I am not sure what MGMAT means by both of its terms?

Is there a faster way to solve x=8 without doing the tedious calculation?

[tim]

i answered this question in your other thread. please don't post the exact same thing twice..