Chapter 8: Problem 55
Solve by completing the square. Show your work. $$ x^{2}+12 x+32=0 $$
Short Answer
Expert verified
The solutions are \( x = -4 \) and \( x = -8 \).
Step by step solution
01
- Rewrite the Equation
First, rewrite the given equation in standard quadratic form if it's not already. The given equation is already in standard form: \[ x^2 + 12x + 32 = 0 \]
02
- Move the Constant Term
Next, move the constant term to the other side of the equation by subtracting 32 from both sides: \[ x^2 + 12x = -32 \]
03
- Find the Value to Complete the Square
To complete the square, take the coefficient of the linear term (12), divide it by 2, and square it. \[ \left( \frac{12}{2} \right)^2 = 6^2 = 36 \]Add 36 to both sides of the equation: \[ x^2 + 12x + 36 = -32 + 36 \]
04
- Simplify Both Sides
Simplify both sides of the equation: \[ x^2 + 12x + 36 = 4 \]
05
- Write as a Perfect Square
The left side of the equation is now a perfect square trinomial. It can be written as the square of a binomial: \[ (x + 6)^2 = 4 \]
06
- Solve for x
To solve for x, take the square root of both sides of the equation: \[ \sqrt{(x + 6)^2} = \pm \sqrt{4} \]This simplifies to: \[ x + 6 = \pm 2 \]
07
- Find the Solutions
Now, solve for x by isolating it on one side of the equation. For the positive case: \[ x + 6 = 2 \] \[ x = 2 - 6 \] \[ x = -4 \]For the negative case: \[ x + 6 = -2 \] \[ x = -2 - 6 \] \[ x = -8 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equations
A quadratic equation is a polynomial equation of the form \(ax^2 + bx + c = 0\). The solutions to a quadratic equation can often be found using various methods like factoring, the quadratic formula, or completing the square. In this exercise, we focus on completing the square, which involves turning a standard quadratic equation into a perfect square trinomial. Understanding the standard form—where \(a = 1\), \(b = 12\), and \(c = 32\) for our equation \(x^2 + 12x + 32 = 0\)—is crucial. All these values play a key role in the steps we perform next.
Perfect Square Trinomial
Completing the square helps us convert a quadratic expression into a perfect square trinomial. Here's how it works with our problem \(x^2 + 12x + 32 = 0\):
Step 1: We start by moving the constant term to the other side \(x^2 + 12x = -32\).
Step 2: We find the value that makes the quadratic a perfect square. Take half the coefficient of the linear term (which is 12), and square it. That gives us \(6^2 = 36\).
Add this value to both sides, transforming the equation into \(x^2 + 12x + 36 = 4\).
Now it’s clear that the left side is a perfect square trinomial, and can be written as \((x + 6)^2 = 4\).
As a perfect square trinomial, it’s easy to solve by taking the square root of both sides.
Step 1: We start by moving the constant term to the other side \(x^2 + 12x = -32\).
Step 2: We find the value that makes the quadratic a perfect square. Take half the coefficient of the linear term (which is 12), and square it. That gives us \(6^2 = 36\).
Add this value to both sides, transforming the equation into \(x^2 + 12x + 36 = 4\).
Now it’s clear that the left side is a perfect square trinomial, and can be written as \((x + 6)^2 = 4\).
As a perfect square trinomial, it’s easy to solve by taking the square root of both sides.
Solving Equations
Once we have a perfect square trinomial, solving the equation becomes straightforward. From our example, we solved by turning \((x + 6)^2 = 4\) into two separate linear equations since \(\text{sqrt}(4) = \text{±2}\). This gives us:
1. \(x + 6 = 2\) - Solve for \(x\), yielding \(x = -4\)
2. \(x + 6 = -2\) - Solve for \(x\), yielding \(x = -8\)
By isolating \(x\) on one side in each case, we identify the solutions to the original quadratic equation. Therefore, the solutions to the initial problem \(x^2 + 12x + 32 = 0\) are \(x = -4\) and \(x = -8\). Understanding these steps highlights the effectiveness of completing the square as an alternative method to solving quadratic equations.
1. \(x + 6 = 2\) - Solve for \(x\), yielding \(x = -4\)
2. \(x + 6 = -2\) - Solve for \(x\), yielding \(x = -8\)
By isolating \(x\) on one side in each case, we identify the solutions to the original quadratic equation. Therefore, the solutions to the initial problem \(x^2 + 12x + 32 = 0\) are \(x = -4\) and \(x = -8\). Understanding these steps highlights the effectiveness of completing the square as an alternative method to solving quadratic equations.