Question

If 'n' is any positive integer>1 then n(2n-1) is always divisible by?
(a) 6 (b) 7 (c) 13 (d) 23

Answer 1

b) Let n= 4
2n-1= 2×4-1
= 8-1= 7

c) let n=7

2n-1=2×7-1

=14-1=13

d)let n= 12

2n-1= 2×12-1

24-1=23
 the correct answer is b c d