Sunday, February 7, 2010

Stephanie's Reflection

tn-t1+(n-1)d (arithmetic)
sn=(n(t1+tn))/2
  • n is term number
  • t1 is first term
  • d is what you add
  • tn is term number in the sequence

tn=t'∙r^(n-1) (geometric)
sn=(t1(1-r^n))/1-r
  • r is what you multiply by

lim/n infinity
  • if the degree of the top is equal to the degree of the bottom then the answer is the coefficient
  • if the degree of the top is greater than the degree of the bottom the answer is infinity
  • if the degree of the top is less than the degree of the bottom the answer is 0
  • if the rules don't apply, use your calculator

for geometric sequences if the absolute value of r is less than 1 then it goes to 0

the sum of infinite series can only be found when a geometric sequence where the absolute value of r is less than 1

s=t1/1-r
  • if the absolute value of r is not less than 1, the series diverges (doesn't approach a number)
  • if the absolute value of r is less than 1, the series approaches a number

1 comment:

  1. Formula: S = t1/1-r

    *can only be found when a geometric sequence where |r|<1

    *if |r| is not less than 1 we say the series diveges - doesn't approach a #

    * if |r|<1 then we say the series approaches a #

    Examples:

    1. Find the sum of the infinite series: 9 - 6 + 4

    (geometric)

    r = -6/9 = -2

    |-2/3| < 1

    S = 9/(1 - (-2/3)) = 27/5

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