find the value of the expression : 1 - 4 + 5 - 8 ... to 50 terms....

• 1-4+5-8.....to 50 terms
  as common diff between 1 and -4 is -3 and +5 and -8 is -3 ,so total 25 terms ...and 25*-3=-75
  or
  1 - 4 + 5 - 8 ... to 50 terms....
  = (1 + 5 + 9 + ... 25 terms) - (4 + 8 + 12 + ... 25 terms)
  = ( 1 + 5 + 9 + ... + 97) - ( 4 + 8 + 12 + ... + 100)
  = [(25/2)(1+97)] -[(25/2)(4+100)]
  = 25(49 - 52)
  = -3*25
  = -75
  
• 11 years agoHelpfull: Yes(1) No(0)
• 1 - 4 + 5 - 8 ... to 50 terms....
  = (1 + 5 + 9 + ... 25 terms) - (4 + 8 + 12 + ... 25 terms)
  = ( 1 + 5 + 9 + ... + 97) - ( 4 + 8 + 12 + ... + 100)
  = [(25/2)(1+97)] + [(25/2)(4+100)]
  = 25(49 + 52)
  = 101 * 25
  = 2525
• 11 years agoHelpfull: Yes(0) No(2)