Chapter 6: Problem 85
Factor each expression completely. \(\left(x^{2}+6 x+9\right)-4 y^{2}\) (Hint: Factor the trinomial in parentheses first.)
Short Answer
Expert verified
The expression factors to \((x + 3 - 2y)(x + 3 + 2y)\).
Step by step solution
01
Recognize the Structure
Notice the expression is written as a difference of two terms. Specifically, \((x^2 + 6x + 9) - 4y^2\), where the first term is a trinomial inside parentheses and the second term is a perfect square \(4y^2\).
02
Factor the Trinomial
Focus on the trinomial \(x^2 + 6x + 9\). This is a perfect square trinomial and can be factored into \((x + 3)^2\). To confirm: expand \((x + 3)^2\) to see if it equals the original trinomial. \((x + 3)(x + 3) = x^2 + 3x + 3x + 9 = x^2 + 6x + 9\).
03
Recognize Difference of Squares
Now replace the trinomial with its factor in the expression: \(((x + 3)^2 - 4y^2)\). This is now a difference of squares, of the form \(a^2 - b^2\), where \(a = (x + 3)\) and \(b = 2y\).
04
Apply Difference of Squares Formula
Use the difference of squares formula: \(a^2 - b^2 = (a - b)(a + b)\). Substitute \(a\) and \(b\) with \((x + 3)\) and \(2y\), respectively. Thus, the expression becomes \((x + 3 - 2y)(x + 3 + 2y)\).
05
Final Expression
Confirm that the expression \((x + 3 - 2y)(x + 3 + 2y)\) is fully factored. There's no further factoring possible for these expressions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Perfect Square Trinomial
A perfect square trinomial is a special type of quadratic expression that can be written in the form \(a^2 + 2ab + b^2\), which factors into \((a + b)^2\). Recognizing these trinomials can make factoring much simpler. For example, in the trinomial \(x^2 + 6x + 9\), we notice that:
- The first term is \(x^2\), which is \(x\) squared.
- The last term is \(9\), which is \(3\) squared.
- The middle term \(6x\) is twice the product of \(x\) and \(3\).
Difference of Squares
The term 'difference of squares' refers to expressions in the form \(a^2 - b^2\). This structure is unique because it can be factored using a specific formula: \(a^2 - b^2 = (a - b)(a + b)\). Recognizing when an expression can be written this way is a powerful factoring skill. Consider \(((x + 3)^2 - 4y^2)\). Here,
- \((x + 3)^2\) represents \(a^2\) in the formula.
- \(4y^2\) is \((2y)^2\), representing \(b^2\).
Step-by-Step Algebra Solutions
Breaking down algebra problems into smaller, more manageable steps is essential for understanding and accuracy. Using a step-by-step approach helps in systematically simplifying and solving algebraic expressions.Here's how the original exercise was tackled:
- Step 1: Identify the structure of the expression as a combination of different forms such as a trinomial and a perfect square.
- Step 2: Factor the trinomial \((x^2 + 6x + 9)\) as a perfect square, \((x + 3)^2\).
- Step 3: Recognize the format of \(a^2 - b^2\) in the new expression \(((x + 3)^2 - 4y^2)\).
- Step 4: Apply the difference of squares formula to factor it into \((x + 3 - 2y)(x + 3 + 2y)\).
- Step 5: Verify that the expression is fully factored and cannot be simplified further.