if z(n)=2s(n)+41 where s(n)=sum of first n natural nos find lowest no for which z(n) is prime??
a)6 b)7 c) 40 d)z(n) is always prime

• answer:-z(n) is always prime.
  z(n)=2s(n)+41
  at n=1, s(n)=1 => z(n)=43
  at n=2, s(n)=3 => z(n)=47
  at n=3, s(n)=6 => z(n)=53
  at n=4, s(n)=10 => z(n)=61
  at n=5, s(n)=15 => z(n)=71
  at n=6, s(n)=21 => z(n)=83
  at n=7, s(n)=28 => z(n)=97
  and so on
• 11 years agoHelpfull: Yes(1) No(0)
• Z is always prime...........
  I agree with Jasmine
• 11 years agoHelpfull: Yes(0) No(0)