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Binomial Theorem. Do you see anything?. 1 1 (n=0) a + b 1 1 (n=1) a 2 + 2ab + b 2 1 2 1 (n=2) a 3 + 3a 2 b + 3ab 2 + b 3 1 3 3 1 (n=3)
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Do you see anything? 1 1 (n=0) a + b 1 1 (n=1) a2+2ab+b2 1 2 1 (n=2) a3+3a2b+3ab2+b3 1 3 3 1 (n=3) a4+4a3b+6a2b2+3ab3+b4 1 4 6 4 1 (n=4) On the left is the expansion by foiling; on the right is something else… Does anyone recognize it? Yes! Pascal’s Triangle!
Lets think a little… When (a+b)4 was expanded, look at it this way: a4 + 4a3b + 6a2b2 + 4ab3 + b4 There was 1 term that no b’s There were 4 terms that had one b There were 6 terms that had two b’s There were 4 terms that had three b’s There was 1 terms that had four b’s.
So now what? Find the following: If your last name begins with A-F find If your last name begins with G-L find If your last name begins with M-P find If your last name begins with Q-S find If your last name begins with T-Z find
What could these represent? 4 terms, 0 (b’s) at a time 4 terms, 1 (b) at a time 4 terms, 2 (b’s) at a time 4 terms, 3 (b’s) at a time 4 terms, 4 (b’s) at a time
Notice anything? That formula allows you to find all the coefficients for a particular row. You found the coefficients for the expansion of (a+b)4 power. Now, what would the coefficients of row 7 be? What do you think would be the easiest way to find it?
Binomial Theorem This all leads us to Binomial Theorem, which allows you to expand any binomial without foiling. Is it better? Depends on the situation, but it is a good process to understand. It is all about patterns! Here is The Binomial Theorem
Binomial Theorem It looks much worse than it is! Don’t worry! The key is patterns – if you notice there is a standard pattern for every term! I’m a fan of
Practice Problems • Evaluate • Expand, then evaluate
Example Given the expansion of Find • The middle term • The second term • The third term • The 9th term
So, if you were giving hints For the middle term the coefficient is…. For the kth term the coefficient is…. why?
Resources • Hubbard, M. , Roby, T., (?) Pascal’s Triangle, from Top to Bottom, retrieved 3/1/05 from http://binomial.csuhayward.edu/Pascal0.html • O'Connor, J. J. , Robertson, E. F. , (1999) Blaise Pascal. Retrieved 2/26/05 fromhttp://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/Pascal.html • Weisstein, Eric W. (?) Pascal’s Triangle, Retrieved 2/26/05 from http://mathworld.wolfram.com/PascalsTriangle.html • Britton, J. (2005) Pascal’s Triangle and its Patterns, Retrieved 3/2/05 http://ccins.camosun.bc.ca/~jbritton/pascal/pascal.html • Katsiavriades, Kryss, Qureshi, Tallaat. (2004) Pascal’s Triangle, Retrieved 2/26/05 from http://www.krysstal.com/binomial.html • Loy, Jim (1999) The Yanghui Triangle, Retrieved 3/1/05 from http://www.jimloy.com/algebra/yanghui.htm • http://mathforum.org/workshops/usi/pascal/pascal_handouts.html