Proving Two Equations Involving nCr and Powers of 2

  • Thread starter Hodgey8806
  • Start date
In summary, for the first proof, you need to use the binomial theorem to show that the sum of r=0 to n [((-1)^r) * (nCr)] equals (1-1)^n, which is equal to 0. For the second proof, you can use the same theorem to show that the sum of r=0 to n [nCr] equals (1+1)^n, which is equal to 2^n.
  • #1
Hodgey8806
145
3

Homework Statement


Prove:
The sum of r=0 to n [((-1)^r) * (nCr)] = 0.

Prove:
The sum of r=0 to n [nCr] = 2^n


Homework Equations


It says to consider (1-1)^n and (1+1)^n , but I have no idea what this is even relating to honestly.


The Attempt at a Solution


I need help getting started.
 
Physics news on Phys.org
  • #2


You do know that
[tex](a+ b)^n= \sum_{r=0}^n \left(\begin{array}{c}n \\ r\end{array}\right)a^{n-r}b^r[/tex]
don't you?
 
  • #3


Yes I do, but I don't know how to apply it. I realize the (1-1)^n is the considered piece for the alternating series. But do I just Induction with it?
 

1. What is the nCr formula and how does it relate to powers of 2?

The nCr formula, also known as the combination formula, is used to calculate the number of ways to choose a subset of r objects from a set of n objects. It is given by nCr = n! / (r!(n-r)!). This formula relates to powers of 2 because the numerator and denominator can be expressed as powers of 2, making it easier to calculate.

2. How can we use nCr and powers of 2 to prove equations?

By using the nCr formula and simplifying it using powers of 2, we can manipulate equations and prove them to be true. For example, we can expand (1+1)^n using the binomial theorem and then compare it to the nCr formula to prove that (1+1)^n = 2^n.

3. Can nCr and powers of 2 be used to solve real-world problems?

Yes, the nCr formula and powers of 2 have various applications in real-world problems, such as calculating the probability of combinations in a deck of cards or the number of ways to form a committee from a group of people. They are also used in computer science and statistics.

4. Are there any limitations to using nCr and powers of 2 in equations?

While nCr and powers of 2 can be useful in solving equations, they may not be applicable to all situations. For example, the nCr formula assumes that all objects are distinguishable, which may not always be the case in real-world problems. Additionally, the powers of 2 may not be the most efficient method in certain calculations.

5. How can we check the accuracy of our proofs involving nCr and powers of 2?

To ensure the accuracy of our proofs, we can use mathematical induction or test our equations with various values of n and r. We can also compare our results to known solutions or use software programs to verify our calculations.

Similar threads

  • Calculus and Beyond Homework Help
Replies
2
Views
703
  • Calculus and Beyond Homework Help
Replies
2
Views
248
  • Calculus and Beyond Homework Help
Replies
1
Views
231
  • Calculus and Beyond Homework Help
Replies
6
Views
466
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
3
Views
802
  • Calculus and Beyond Homework Help
Replies
1
Views
501
  • Calculus and Beyond Homework Help
Replies
4
Views
283
  • Calculus and Beyond Homework Help
Replies
6
Views
365
  • Calculus and Beyond Homework Help
Replies
3
Views
506
Back
Top