Show that the permutations of the letters of the word AMERICA is the same as the permutations of the letters of the word CALCUTTA. Expand (x - 2)^9 and find the sixth term using th... Show that the permutations of the letters of the word AMERICA is the same as the permutations of the letters of the word CALCUTTA. Expand (x - 2)^9 and find the sixth term using the Binomial theorem.

Question image

Understand the Problem

The question is asking to prove a statement regarding the permutations of letters in certain words and to perform an expansion using the binomial theorem, which involves calculations and theoretical proof.

Answer

The sixth term in the expansion of $(x - 2)^{99}$ is $$ T_6 = -32 \cdot \binom{99}{5} x^{94} $$
Answer for screen readers

The sixth term in the expansion of $(x - 2)^{99}$ is:

$$ T_6 = -32 \cdot \binom{99}{5} x^{94} $$

Steps to Solve

  1. Understanding the Problem
    We need to expand the expression $(x - 2)^{99}$ using the Binomial Theorem and find the sixth term in the expansion.

  2. Using the Binomial Theorem
    According to the Binomial Theorem, the expansion of $(a + b)^n$ is given by:

$$ \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k $$

For our case, we have (a = x), (b = -2), and (n = 99).

  1. Identifying the Sixth Term
    The $k^{th}$ term in the expansion can be written as:

$$ T_{k+1} = \binom{n}{k} a^{n-k} b^k $$

To find the sixth term, we set (k = 5):

$$ T_6 = \binom{99}{5} x^{99-5} (-2)^5 $$

  1. Calculating the Binomial Coefficient
    We calculate the binomial coefficient:

$$ \binom{99}{5} = \frac{99!}{5! \cdot (99-5)!} $$

  1. Calculating the Powers
    Next, calculate the powers:

$$ x^{99-5} = x^{94} $$

And for (b^5):

$$ (-2)^5 = -32 $$

  1. Putting It All Together
    Now, combine all parts together to express (T_6):

$$ T_6 = \binom{99}{5} x^{94} (-32) $$

  1. Final Calculation
    Now we compute:

$$ T_6 = -32 \cdot \binom{99}{5} x^{94} $$

We can leave the answer in terms of the binomial coefficient.

The sixth term in the expansion of $(x - 2)^{99}$ is:

$$ T_6 = -32 \cdot \binom{99}{5} x^{94} $$

More Information

The binomial coefficient (\binom{99}{5}) represents the number of ways to choose 5 items from 99, and is commonly used in combinatorics. Using the Binomial Theorem allows us to simplify the expansion of polynomial expressions efficiently.

Tips

  • Confusing term numbers: Remember that the sixth term corresponds to (k = 5) since we start counting (k) from 0.
  • Sign errors: Be cautious of negative signs, especially when raising negative numbers to powers.

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