Q.

Among the statements

(S1):20232022-19992022 is divisible by 8

(S2):13(13)n-11n-13 is divisible by 144 for infinitely many n                [2023]

1 only (S2) is correct  
2 both (S1) and (S2) are incorrect  
3 both (S1) and (S2) are correct  
4 only (S1) is correct  

Ans.

(3)

As we know that xn-yn is always divisible by x-y

  20232022-19992022 is divisible by 2023 - 1999 = 24, which is divisible by 8.       S1 is true.

Also, 13(13)n-11n-13=13(12+1)n-11n-13

=13[C0n12n+C1n12n-1+C2n12n-2++Cnn]-11n-13

=13[C0n12n+C1n12n-1++Cn-2n122]+13·12·n+13-11n-13

=13×122[C0n12n-2+C1n12n-3++Cn-2n]+145n

Which is divisible by 144, for all n144.

i.e., It is divisible by 144 for infinitely many nN.

   S2 is also true.