-1^2+2^2-3^2+4^2..........-17^2+18^2 =

1) 171
2) 342
3) 513
4) 473

• 1) 171
  
  -1^2+2^2-3^2+4^2..........-17^2+18^2 = (2^2-1^2)+(4^2-3^2)+...+(18^2-17^2)
  = 3+7+11+....+35 ... total 9 terms of AP
  = (9/2)*(3+35)=9*19=171
• 11 years agoHelpfull: Yes(0) No(0)