Chapter 15: Problem 50
Use the binomial theorem to expand each expression. $$\left(t^{2}-\frac{1}{2} u\right)^{4}$$
Short Answer
Expert verified
The short version of the answer is:
\[\left(t^2-\frac{1}{2}u\right)^4 = t^8 - 2t^6u + \frac{3}{2}t^4u^2 - \frac{1}{2}t^2u^3 + \frac{1}{16}u^4\]
Step by step solution
01
Identify the expression to expand
We have the following expression to expand:
\[\left(t^{2}-\frac{1}{2}u\right)^4\]
02
Apply the binomial theorem
Using the binomial theorem, we can write the expression as:
\[\left(t^{2} - \frac{1}{2}u\right)^4 = \sum_{k=0}^{4} \binom{4}{k} (t^2)^{4-k} \left(-\frac{1}{2}u\right)^k \]
03
Calculate the binomial coefficients and expand each term
Now, we will calculate the binomial coefficients and expand each term in the sum:
\[\binom{4}{0} = 1\]
\[\binom{4}{1} = 4\]
\[\binom{4}{2} = 6\]
\[\binom{4}{3} = 4\]
\[\binom{4}{4} = 1\]
Then, we find each term of the sum:
\[1 \cdot (t^{2})^{4-0} \cdot \left(-\frac{1}{2}u\right)^0 = t^8\]
\[4 \cdot (t^{2})^{4-1} \cdot \left(-\frac{1}{2}u\right)^1 = -4t^6\cdot \frac{1}{2} u = -2t^6u\]
\[6 \cdot (t^{2})^{4-2} \cdot \left(-\frac{1}{2}u\right)^2 = 6t^4 \cdot \frac{1}{4} u^2 = \frac{3}{2}t^4u^2\]
\[4 \cdot (t^{2})^{4-3} \cdot \left(-\frac{1}{2}u\right)^3 = 4t^2 \cdot -\frac{1}{8} u^3 = -\frac{1}{2} t^2u^3\]
\[1 \cdot (t^{2})^{4-4} \cdot \left(-\frac{1}{2}u\right)^4 = \frac{1}{16}u^4\]
04
Combine the terms
Combining all terms, we have the expanded expression:
\[\left(t^2-\frac{1}{2}u\right)^4 = t^8 - 2t^6u + \frac{3}{2}t^4u^2 - \frac{1}{2}t^2u^3 + \frac{1}{16}u^4\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Algebraic Expansion
Algebraic expansion is a technique used to simplify expressions by breaking them down into simpler terms. This often involves expressions raised to a power, like \((t^2 - \frac{1}{2}u)^4\). The goal is to expand these expressions into a sum of terms, each easier to manage. In the case of binomial expressions, the binomial theorem serves as a powerful tool to achieve this expansion. By systematically applying the theorem, we convert a compact expression into a standard polynomial form.
- Start with identifying the base expression.
- Then, apply the expansion method to break it down.
- The result is a series of terms that comprise the simplified form of the expression.
Binomial Coefficients
Binomial coefficients are numbers that occur in the process of expanding a binomial raised to a power. These coefficients can be found in Pascal's Triangle or calculated using the formula: \[ \binom{n}{k} = \frac{n!}{k!(n-k)!} \] where \(n\) is the power and \(k\) is the term number in the expansion. In the expansion \( (t^{2} - \frac{1}{2}u)^4 \), these coefficients provide the weights for each term in the expansion:
- \( \binom{4}{0} = 1 \)
- \( \binom{4}{1} = 4 \)
- \( \binom{4}{2} = 6 \)
- \( \binom{4}{3} = 4 \)
- \( \binom{4}{4} = 1 \)
Polynomial Expressions
A polynomial expression is a sum of multiple terms, each consisting of a constant coefficient multiplied by a variable raised to a power. Expanding \((t^2 - \frac{1}{2}u)^4\) results in a polynomial expression where each term involves different powers of \(t^2\) and \(-\frac{1}{2}u\). Here's how the polynomial expansion looks:
- \( t^8 \)
- \( -2t^6u \)
- \( \frac{3}{2}t^4u^2 \)
- \( -\frac{1}{2}t^2u^3 \)
- \( \frac{1}{16}u^4 \)
Mathematical Calculation
Mathematical calculation involves performing various steps to achieve accurate results from an expression or problem. Let's break it down with the binomial expansion:
- Use the binomial theorem to formulate the \(n\)th power of the expression.
- Determine each binomial coefficient accordingly.
- Substitute these coefficients and expressions into the expansion formula.
- Carefully calculate each term. Remember to handle signs and fractions appropriately.
- Finally, sum up all terms to complete the expansion.