sahilanand's blog

By sahilanand, history, 2 years ago, In English

Arithmetic Sequence:-

  • The sequence in which each consecutive terms has a same common difference.
  • Eg:-0, 2, 4, 6, 8,...
  • a is the first term of the sequence, d is the common difference and n is no. of terms
  • To find the nth term of AP:an = a+(n-1)*d
  • To find the sum of the AP: Sn = (n/2)*[2a + (n-1)*d]
  • = (n/2)*[a + {a + (n-1)*d}] [: expression in angular bracket is an]
  • = (n/2)*(af+al)
  • Hence, the sum of AP can also be written as: Sn = (n/2)*(af+al) [:af=first term & al=last term]

Geometric Sequence:-

  • The sequence in which each consecutive term has a common ratio.
  • Eg:-1, 5, 25, 125,...
  • a is the first term of the sequence, r is the common ratio and n is no. of terms
  • To find the nth term of GP:an = (a * r^(n-1))
  • To find the sum of the GP: Sn = a * {[r^(n-1)-1]/[r-1]}

Harmonic Sequence:-

  • The sequence in which the reciprocal of each term forms an arithmetic sequence.
  • Eg:-(1/2),(1/4),(1/6),(1/8),...
  • Summation for Harmonic Sequence:
  • a is the first term of the sequence, d is the common difference and n is no. of terms
  • To find the nth term of AP:an = {1 / [a+b*(n-1)]}

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