Chapter 6: Problem 20
Find the indicated products directly by inspection. It should not be necessary to write down intermediate steps [except possibly when using Eq. (6.6) ] $$(9 a+8 b)^{2}$$
Short Answer
Expert verified
The product is \(81a^2 + 144ab + 64b^2\).
Step by step solution
01
Identify the Binomial Formula
The given expression \((9a + 8b)^2\) is a square of a binomial. We can use the binomial square formula: \((x + y)^2 = x^2 + 2xy + y^2\), where \(x = 9a\) and \(y = 8b\).
02
Compute the First Square Term
According to the formula, compute the square of the first term \(x^2 = (9a)^2\). This results in \(81a^2\).
03
Compute the Middle Term
Now, compute the middle term using \(2xy = 2(9a)(8b) = 144ab\).
04
Compute the Second Square Term
Lastly, compute the square of the second term \(y^2 = (8b)^2\). This results in \(64b^2\).
05
Construct the Final Expression
Combine all the terms from Steps 2, 3, and 4 to form the expanded expression: \((9a + 8b)^2 = 81a^2 + 144ab + 64b^2\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Square of a Binomial
The square of a binomial refers to multiplying a binomial by itself. A binomial is an algebraic expression consisting of two terms, such as \((x + y)\). When you square a binomial, you use the formula:\((x + y)^2 = x^2 + 2xy + y^2\). This formula helps quickly expand expressions without multiple distribution steps. Let's break this down:
- \(x^2\) represents squaring the first term.
- \(2xy\) represents twice the product of both terms.
- \(y^2\) represents squaring the second term.
Algebraic Expressions
Algebraic expressions are mathematical phrases that can contain numbers, variables, and operation symbols. They help in forming equations and modeling real-world situations. In algebra, expressions like \(9a + 8b\) are used frequently, where
- "\(a\)" and "\(b\)" are variables representing unknown values.
- "9" and "8" are coefficients that multiply the variables.
Polynomials
Polynomials are expressions consisting of multiple terms. They can include variables raised to powers or exponents. A polynomial can be classified by its number of terms or the degree of its terms. For instance, in the expression\((9a + 8b)\) longer form \(81a^2 + 144ab + 64b^2\), we see:
- "\(81a^2\)" is a term where "\(a\)" is raised to the power of 2, indicating it's a quadratic term.
- "\(144ab\)" is a linear term involving two variables.
- "\(64b^2\)" is another quadratic term.
Mathematical Formulas
Mathematical formulas are concise ways of expressing mathematical truths or relationships. They provide a quick reference for various mathematical operations. In algebra, formulas simplify complex calculations by reducing them to a few steps.The binomial square formula \((x+y)^2 = x^2 + 2xy + y^2\) is a prime example of a formula simplifying the binomial expansion. It allows you to handle expanding binomials effectively without writing each step involved in multiplication.Other common algebraic formulas include:
- The quadratic formula: \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]
- The difference of squares: \((x-y)(x+y) = x^2 - y^2\)