Thursday, March 20, 2014

Board Building: Massimo Banzi, Arduino

What Computers Do: Model, Connect, and Engage

What Computers Do: Model, Connect, and Engage

5 Ways to Solve Recurrence Relations - wikiHow

5 Ways to Solve Recurrence Relations - wikiHow:



Edited by Peter, Molly, Jason, Teresa and 10 others
In trying to find a formula for some mathematical sequence, a common intermediate step is to find the nth term, not as a function of n, but in terms of earlier terms of the sequence. For example, while it'd be nice to have a closed form function for the nth term of the Fibonacci sequence, sometimes all you have is the recurrence relation, namely that each term of the Fibonacci sequence is the sum of the previous two terms. This article will present several methods for deducing a closed form formula from a recurrence.

Method 1 of 5: Arithmetic

  1. Solve Recurrence Relations Step 1 Version 2.jpg
    1
    Consider an arithmetic sequence such as 5, 8, 11, 14, 17, 20, ....
  2. Solve Recurrence Relations Step 2 Version 2.jpg
    2
    Since each term is 3 larger than the previous, it can be expressed as a recurrence as shown.
  3. Solve Recurrence Relations Step 3 Version 2.jpg
    3
    Recognize that any recurrence of the form an = an-1 + d is an arithmetic sequence.
  4. Solve Recurrence Relations Step 4 Version 2.jpg
    4
    Write the closed-form formula for an arithmetic sequence, possibly with unknowns as shown.
  5. Solve Recurrence Relations Step 5 Version 2.jpg
    5
    Solve for any unknowns depending on how the sequence was initialized. In this case, since 5 was the 0th term, the formula is an = 5 + 3n. If instead, you wanted 5 to be the first term, you would get an = 2 + 3n.


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Monday, March 10, 2014

Ban Bossy. Encourage Girls to Lead

Ban Bossy. Encourage Girls to Lead:



When a little boy asserts himself, he's called a “leader.” Yet when a little girl does the same, she risks being branded “bossy.” Words like bossy send a message: don't raise your hand or speak up. By middle school, girls are less interested in leading than boys—a trend that continues into adulthood. Together we can encourage girls to lead.



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