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.

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
-
Understanding the Problem
We need to expand the expression $(x - 2)^{99}$ using the Binomial Theorem and find the sixth term in the expansion. -
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).
- 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):
$$ T_6 = \binom{99}{5} x^{99-5} (-2)^5 $$
- Calculating the Binomial Coefficient
We calculate the binomial coefficient:
$$ \binom{99}{5} = \frac{99!}{5! \cdot (99-5)!} $$
- Calculating the Powers
Next, calculate the powers:
$$ x^{99-5} = x^{94} $$
And for (b^5):
$$ (-2)^5 = -32 $$
- Putting It All Together
Now, combine all parts together to express (T_6):
$$ T_6 = \binom{99}{5} x^{94} (-32) $$
- 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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