Problem 42 - College Algebra

Question

Factor the difference of two squares. $$ 64 x^{2}-81 $$

Step-by-Step Solution

Answer

The factored form of \(64x^{2} - 81\) is \((8x - 9)(8x + 9)\).

Step 1: Identify a and b

In the given problem, the expression is \(64x^{2} - 81\). Therefore, \(a = 8x\) and \(b = 9\), as \(8x\) squared is \(64x^{2}\) and \(9\) squared is \(81\).

Step 2: Apply the difference of squares formula

Apply the formula \(a^{2} - b^{2} = (a - b)(a + b)\) by substituting \(a = 8x\) and \(b = 9\). Thus, the difference of squares becomes \((8x - 9)(8x + 9)\).

Key Concepts

Factoring Polynomials

Factoring polynomials is a fundamental skill in algebra, involving the process of breaking down a polynomial into simpler components, known as factors, that when multiplied together give back the original polynomial. One common technique for factoring is the recognition of the difference of two squares - a special case that occurs when a polynomial is composed of exactly two terms, both of which are perfect squares, separated by a subtraction sign.

To practice factoring polynomials, let's consider the algebraic expression \(64x^{2} - 81\). Notice how both terms are perfect squares, as \(64x^{2}\) can be rewritten as \(8x\) squared, and \(81\) as \(9\) squared. By applying the difference of two squares formula \(a^{2} - b^{2} = (a - b)(a + b)\), where \(a\) and \(b\) are any real numbers or algebraic expressions, we can write the expression as \( (8x - 9)(8x + 9)\), thus factoring the polynomial into simpler binomial components.

Algebraic Expressions

Algebraic expressions are combinations of variables, numbers, and operations. In the case of our exercise, \(64x^{2} - 81\) is such an expression. The expression includes a variable \(x\), constants \(64\) and \(81\), and the operation of subtraction. Understanding how to manipulate these expressions is crucial in algebra.

Expressions can be simplified or transformed through various methods such as factoring, which helps in solving equations, simplifying calculations, and understanding relationships between variables. For instance, factoring out the expression \(64x^{2} - 81\) illuminates its inherent properties, showing it is composed of two factors that can be further analyzed individually.

Quadratic Equations

Quadratic equations are a type of polynomial equation of the second degree, typically in the form \(ax^{2} + bx + c = 0\), where \(a\), \(b\), and \(c\) are constants, and \(a \eq 0\). They can often be solved by factoring, completing the square, using the quadratic formula, or graphing.

The expression \(64x^{2} - 81\) can be considered as the left side of a quadratic equation set to zero: \(64x^{2} - 81 = 0\). Solving for \(x\) means factoring the expression and then finding the values of \(x\) that make each factor equal to zero. In our case, setting \(8x - 9 = 0\) would yield \(x = 9/8\) and setting \(8x + 9 = 0\) would yield \(x = -9/8\), giving us the solutions to the corresponding quadratic equation.