Looking for reliable answers? Westonci.ca is the ultimate Q&A platform where experts share their knowledge on various topics. Get detailed answers to your questions from a community of experts dedicated to providing accurate information. Discover in-depth answers to your questions from a wide network of professionals on our user-friendly Q&A platform.

Evaluate the expression:

[tex]\[ 3^{17} C_{17}^0 - 4 \times 3^{16} C_{17}^1 + 4^2 \times 3^{15} C_{17}^2 - 4^3 \times 3^{14} C_{17}^3 + \ldots - 4^{17} C_{17}^{17} \][/tex]


Sagot :

To solve the given expression:

[tex]\[ 3^{17} \binom{17}{0} - 4 \cdot 3^{16} \binom{17}{1} + 4^2 \cdot 3^{15} \binom{17}{2} - 4^3 \cdot 3^{14} \binom{17}{3} + \ldots - 4^{17} \binom{17}{17} \][/tex]

we will proceed step-by-step.

1. Identify the General Form: The expression is a combination of powers of 3 and 4, and binomial coefficients [tex]\(\binom{17}{i}\)[/tex]. It alternates in sign and follows a pattern. The general term can be represented as:
[tex]\[ (-1)^i \cdot 4^i \cdot 3^{17-i} \cdot \binom{17}{i} \][/tex]
for [tex]\(i\)[/tex] ranging from 0 to 17.

2. Sum of the Series: The sum we want to calculate is:
[tex]\[ \sum_{i=0}^{17} (-1)^i \cdot 4^i \cdot 3^{17-i} \cdot \binom{17}{i} \][/tex]

3. Factor Out Common Terms:
Notice that [tex]\(3^{17}\)[/tex] is a common factor across all terms when factored correctly. We can factor it out:
[tex]\[ 3^{17} \sum_{i=0}^{17} \left( \frac{4}{3} \right)^i \cdot (-1)^i \cdot \binom{17}{i} \][/tex]

4. Simplify the Series:
We recognize that this sum is related to the binomial expansion of [tex]\( (1 + x)^n \)[/tex] for [tex]\( x = -\frac{4}{3} \)[/tex]:
[tex]\[ \sum_{i=0}^{n} \binom{n}{i} x^i = (1+x)^n \][/tex]

Here, [tex]\( x = -\frac{4}{3} \)[/tex] and [tex]\( n = 17 \)[/tex]:
[tex]\[ \sum_{i=0}^{17} \binom{17}{i} \left( -\frac{4}{3} \right)^i = \left( 1 - \frac{4}{3} \right)^{17} \][/tex]

5. Simplify the Exponent:
Simplify the term within the parentheses:
[tex]\[ 1 - \frac{4}{3} = -\frac{1}{3} \][/tex]

Raise this to the power of 17:
[tex]\[ \left( -\frac{1}{3} \right)^{17} = -\frac{1}{3^{17}} \][/tex]

6. Final Calculation:
Substitute this back into our factored expression:
[tex]\[ 3^{17} \sum_{i=0}^{17} \left( \frac{4}{3} \right)^i \cdot (-1)^i \cdot \binom{17}{i} = 3^{17} \cdot \left( -\frac{1}{3^{17}} \right) = 3^{17} \cdot -\frac{1}{3^{17}} = -1 \][/tex]

Thus, the result of the given series is:
[tex]\[ \boxed{-1} \][/tex]
Thank you for your visit. We're committed to providing you with the best information available. Return anytime for more. Thank you for choosing our platform. We're dedicated to providing the best answers for all your questions. Visit us again. We're glad you chose Westonci.ca. Revisit us for updated answers from our knowledgeable team.