find the sum upto n terms
10+84+734+.....

• 10+84+734+....
  =(9+1)+(9^2+3)+(9^3+5)+...
  =(9+9^2+9^3+...)+(1+3+5+7+...)
  =9(9^n-1)/(9-1)+n^2
  [sum of Geometric progression=a(r^n -1)/(r-1) & sum of first n odd no.=n^2]
  =9(9^n-1)/8)+n^2
• 10 years agoHelpfull: Yes(22) No(0)
• i think the naswer is (9^n+(2n-1)).here 9^n will give the powers for 9 for different n say 1,2,3,4.(2n-1) will give the prime numbers for differtn value of n say 1,3,5,7.on adding we get the sequence
• 10 years agoHelpfull: Yes(3) No(1)
• 9(9^n-1)/8 + n^2
  
  Put value n=0,1... to check!
• 10 years agoHelpfull: Yes(1) No(1)
• 10=9+1
  84=9^2+3
  734=9^3+5
  so=6568=9^4+7 [ANS]
• 9 years agoHelpfull: Yes(0) No(1)