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The sum of the infinite and finite geometric sequence

The sum of the infinite and finite geometric sequence. The sum of the first n terms of a sequence is represented by summation notation . . upper limit of summation. lower limit of summation. index of summation. 2. The sum of a finite geometric sequence is given by .

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The sum of the infinite and finite geometric sequence

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  1. The sum of the infinite and finite geometric sequence

  2. The sum of the first n terms of a sequence is represented by summation notation. upper limit of summation lower limit of summation index of summation 2

  3. The sum of a finite geometric sequence is given by 5 + 10 + 20 + 40 + 80 + 160 + 320 + 640 = ? n = 8 a1 = 5

  4. has the sum The sum of the terms of an infinite geometric sequence is called a geometric series. If |r| < 1, then the infinite geometric series a1 + a1r + a1r2 + a1r3 + . . . + a1rn-1 + . . .

  5. The sum of the series is Example: Find the sum of

  6. Convergent and Divergent Series

  7. Convergent and Divergent Series • If the infinite series has a sum, or limit, the series is convergent. • If the series is not convergent, it is divergent.

  8. Ways To Determine Convergence/Divergence • 1. Arithmetic – since no sum exists, it diverges • 2. Geometric: • If |r| > 1, diverges • If |r| < 1, converges since the sum exists 3. Ratio Test (discussed in a few minutes)

  9. Example Determine whether each arithmetic or geometric series is convergent or divergent. • 1/8 + 3/20 + 9/50 + 27/125 + . . . • r=6/5  |r|>1  divergent • 18.75+17.50+16.25+15.00+ . . . • Arithmetic series  divergent • 65 + 13 + 2 3/5 + 13/25 . . . • r=1/5  |r|<1  convergent

  10. Other Series • When a series is neither arithmetic or geometric, it is more difficult to determine whether the series is convergent or divergent.

  11. Ratio Test In the ratio test, we will use a ratio of an and an+1 to determine the convergence or divergence of a series. Leading coefficient is a Review: Leading coefficient is d Denominator degree is greater

  12. Test for convergence or divergence of: Since this ratio is less than 1, the series converges.

  13. Test for convergence or divergence of: The ratio of the leading coefficients is 1 Since this ratio is less than 1, the series converges.

  14. Test for convergence or divergence of: Coefficient of n2 is 1 Since this ratio is 1, the test is inconclusive. Coefficient of n2 is 1

  15. Example • Use the ratio test to determine if the series is convergent or divergent. 1/2 + 2/4 + 3/8 + 4/16 + . . . Since r<1, the series is convergent.

  16. Example • Use the ratio test to determine if the series is convergent or divergent. 1/2 + 2/3 + 3/4 + 4/5 + . . . Since r=1, the ratio test provides no information.

  17. Example • Use the ratio test to determine if the series is convergent or divergent. 2 + 3/2 + 4/3 + 5/4 + . . . Since r=1, the ratio test provides no information.

  18. Example • Use the ratio test to determine if the series is convergent or divergent. 3/4 + 4/16 + 5/64 + 6/256 + . . . Since r<1, the series is convergent.

  19. Example • Use the ratio test to determine if the series is convergent or divergent. Since r<1, the series is convergent.

  20. Example • Use the ratio test to determine if the series is convergent or divergent. Since r>1, the series is divergent.

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