Chapter 9: Problem 24
Use the binomial theorem to expand and simplify. $$(2 t-s)^{5}$$
Short Answer
Expert verified
The expansion of \((2t - s)^5\) is \(32t^5 - 80t^4s + 80t^3s^2 - 40t^2s^3 + 10ts^4 - s^5\).
Step by step solution
01
Identify Parameters
The binomial theorem states that \[(a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^k\]For the expression \((2t - s)^5\), consider it as \((2t + (-s))^5\). Here, \(a = 2t\), \(b = -s\), and \(n = 5\).
02
Expand using Binomial Coefficients
Apply the binomial theorem to expand:\[(2t - s)^5 = \sum_{k=0}^{5} \binom{5}{k} (2t)^{5-k} (-s)^k\]Compute each term separately.
03
Calculate Each Term
Calculate each term in the expansion:\[\begin{align*}\text{Term } k=0: & \quad \binom{5}{0} (2t)^5 (-s)^0 = 1 \times (32t^5) \times 1 = 32t^5 \\text{Term } k=1: & \quad \binom{5}{1} (2t)^4 (-s)^1 = 5 \times (16t^4) \times (-s) = -80t^4s \\text{Term } k=2: & \quad \binom{5}{2} (2t)^3 (-s)^2 = 10 \times (8t^3) \times s^2 = 80t^3s^2 \\text{Term } k=3: & \quad \binom{5}{3} (2t)^2 (-s)^3 = 10 \times (4t^2) \times (-s^3) = -40t^2s^3 \\text{Term } k=4: & \quad \binom{5}{4} (2t)^1 (-s)^4 = 5 \times (2t) \times s^4 = 10ts^4 \\text{Term } k=5: & \quad \binom{5}{5} (2t)^0 (-s)^5 = 1 \times 1 \times (-s^5) = -s^5 \\end{align*}\]
04
Combine All Terms
Now, compile all the terms and simplify the expression:\[32t^5 - 80t^4s + 80t^3s^2 - 40t^2s^3 + 10ts^4 - s^5\]This is the simplified expansion of \((2t - s)^5\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Polynomial Expansion
The process of expanding a polynomial entails breaking it down into a series of terms. Each term is a simpler expression of the variables involved. The original problem gives us \((2t - s)^5\), which needs expression in expanded form.Expanding a polynomial like this involves:
- Identifying each component of the expression. Here, 2t and -s.
- Applying algebraic rules to rewrite it as a sum of terms.
Binomial Coefficients
A binomial coefficient specifies the number of ways to choose 'k' elements from a set of 'n' elements, denoted as \(\binom{n}{k}\). These coefficients appear naturally in the expansion of expressions raised to a power, like in our problem.Calculating binomial coefficients involves:
- Identifying the order of the expression, which is 5 in this case.
- Using the formula \(\binom{5}{k}\), for each k, where k ranges from 0 to n (5 in this exercise).
Algebraic Expressions
Algebraic expressions consist of variables, coefficients, and operators like plus or minus signs. They're used to represent real-world quantities and their relationships abstractly.The original expression \((2t - s)^5\) is a perfect example.The form of an algebraic expression:
- Variables: In our problem, t and s.
- Constants and coefficients: Numbers multiplying the variables like 2 in 2t or -1 in -s.
- Operators: Terms connected by '+' or '-'.