{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

# 222a4s - MATH 222 FALL 2011 Assignment Four(Answer Key 1...

This preview shows pages 1–2. Sign up to view the full content.

MATH 222 FALL 2011, Assignment Four (Answer Key) 1. For n 1, let b n denote the number of ways to express n as the sum of 1s and 2s, taking order into account. Thus, b 4 = 5 because 4 = 1 + 1 + 1 + 1 = 2 + 2 = 2 + 1 + 1 = 1 + 1 + 2 = 1 + 2 + 1. (a) Find the first five terms of the sequence { b n } . b 1 = 1 ,b 2 = 2 ,b 3 = 3 ,b 4 = 5 ,b 5 = 8 (b) Find a recursive definition for b n . Divide all expressions S n of n as sum of 1s and 2s into two groups S 1 n and S 2 n where S 1 n consists of those whose last summand is 1 and S 2 n consists those whose last summand is 2. We have | S n | = b n , | S 1 n | = b n - 1 and | S 2 n | = b n - 2 for each n 3, so b n = b n - 1 + b n - 2 , i.e., the sequence { b n } satisfies the Fibonacci recurrence equation. 2. Find the sequence whose generating function is x 1 - 2 x 2 . x 1 - 2 x 2 = x i =0 (2 x 2 ) i = i =0 2 i x 2 i +1 = j =0 2 j - 3 2 [1 - ( - 1) j ] x j So the sequence is 2 j - 3 2 [1 - ( - 1) j ], j 0. 3. Use generating functions to solve the following problems: (a) How many integer solutions are there to x 1 + x 2 + x 3 + x 4 = 30 , x 1 1 , x 2 2 , x 3 3 , x 4 4?

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern