Solve by completing the square, show all work: 2x2 - 8x -5 = 0

Algebra and Trigonometry (6th Edition)
6th Edition
ISBN:9780134463216
Author:Robert F. Blitzer
Publisher:Robert F. Blitzer
ChapterP: Prerequisites: Fundamental Concepts Of Algebra
Section: Chapter Questions
Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
Question
### Question 10

**Solve by completing the square, show all work:**

\[2x^2 - 8x - 5 = 0\]

#### Solution Steps:

1. **Divide the entire equation by the coefficient of \(x^2\):**

   \[\frac{2x^2 - 8x - 5}{2} = \frac{0}{2}\]
   \[x^2 - 4x - \frac{5}{2} = 0\]

2. **Isolate the constant term:**

   \[x^2 - 4x = \frac{5}{2}\]

3. **Complete the square:**
   - Take the coefficient of \(x\) (which is \(-4\)), divide it by 2, and square it:
   
     \[\left(\frac{-4}{2}\right)^2 = (-2)^2 = 4\]

   - Add and subtract this value on the left-hand side of the equation:

     \[x^2 - 4x + 4 - 4 = \frac{5}{2}\]
     \[x^2 - 4x + 4 = \frac{5}{2} + 4\]
     \[x^2 - 4x + 4 = \frac{5}{2} + \frac{8}{2}\]
     \[x^2 - 4x + 4 = \frac{13}{2}\]

   - Now, express the left-hand side as a perfect square:

     \[(x-2)^2 = \frac{13}{2}\]

4. **Solve the resulting equation:**

   - Take the square root of both sides:

     \[x - 2 = \pm \sqrt{\frac{13}{2}}\]

   - Simplify:

     \[x - 2 = \pm \frac{\sqrt{26}}{2}\]

   - Solve for \(x\):

     \[x = 2 \pm \frac{\sqrt{26}}{2}\]

5. **Write the final answer:**

   \[x = 2 + \frac{\sqrt{26}}{2}\]
   \[x = 2 - \frac{\sqrt{26}}{2}\]

Thus, the solutions to the equation \(2x^2 -
Transcribed Image Text:### Question 10 **Solve by completing the square, show all work:** \[2x^2 - 8x - 5 = 0\] #### Solution Steps: 1. **Divide the entire equation by the coefficient of \(x^2\):** \[\frac{2x^2 - 8x - 5}{2} = \frac{0}{2}\] \[x^2 - 4x - \frac{5}{2} = 0\] 2. **Isolate the constant term:** \[x^2 - 4x = \frac{5}{2}\] 3. **Complete the square:** - Take the coefficient of \(x\) (which is \(-4\)), divide it by 2, and square it: \[\left(\frac{-4}{2}\right)^2 = (-2)^2 = 4\] - Add and subtract this value on the left-hand side of the equation: \[x^2 - 4x + 4 - 4 = \frac{5}{2}\] \[x^2 - 4x + 4 = \frac{5}{2} + 4\] \[x^2 - 4x + 4 = \frac{5}{2} + \frac{8}{2}\] \[x^2 - 4x + 4 = \frac{13}{2}\] - Now, express the left-hand side as a perfect square: \[(x-2)^2 = \frac{13}{2}\] 4. **Solve the resulting equation:** - Take the square root of both sides: \[x - 2 = \pm \sqrt{\frac{13}{2}}\] - Simplify: \[x - 2 = \pm \frac{\sqrt{26}}{2}\] - Solve for \(x\): \[x = 2 \pm \frac{\sqrt{26}}{2}\] 5. **Write the final answer:** \[x = 2 + \frac{\sqrt{26}}{2}\] \[x = 2 - \frac{\sqrt{26}}{2}\] Thus, the solutions to the equation \(2x^2 -
### Question 9

**Problem Statement:**  
Solve by completing the square, show all work:

\[ x^2 - 6x = 13 \]

**Solution:**  
To solve the equation \( x^2 - 6x = 13 \) by completing the square, follow these steps:

1. **Move the constant term to the right side of the equation:**
   
   \[ x^2 - 6x + \_ = 13 + \_ \]

2. **Complete the square on the left side of the equation:**
   
   To complete the square, add the square of half the coefficient of \( x \). The coefficient of \( x \) is \(-6\), and half of that is \(-3\). The square of \(-3\) is \(9\).

   \[ x^2 - 6x + 9 = 13 + 9 \]
   \[ x^2 - 6x + 9 = 22 \]

3. **Rewrite the left side of the equation as a squared binomial:**
   
   \[ (x - 3)^2 = 22 \]

4. **Solve for \( x \):**
   
   Take the square root of both sides of the equation:
   
   \[ x - 3 = \pm \sqrt{22} \]

5. **Isolate \( x \):**
   
   \[ x = 3 \pm \sqrt{22} \]

Therefore, the solutions to the equation \( x^2 - 6x = 13 \) are:

\[ x = 3 + \sqrt{22} \quad \text{or} \quad x = 3 - \sqrt{22} \]

### Final Answer:
The solutions are \( x = 3 + \sqrt{22} \) and \( x = 3 - \sqrt{22} \).
Transcribed Image Text:### Question 9 **Problem Statement:** Solve by completing the square, show all work: \[ x^2 - 6x = 13 \] **Solution:** To solve the equation \( x^2 - 6x = 13 \) by completing the square, follow these steps: 1. **Move the constant term to the right side of the equation:** \[ x^2 - 6x + \_ = 13 + \_ \] 2. **Complete the square on the left side of the equation:** To complete the square, add the square of half the coefficient of \( x \). The coefficient of \( x \) is \(-6\), and half of that is \(-3\). The square of \(-3\) is \(9\). \[ x^2 - 6x + 9 = 13 + 9 \] \[ x^2 - 6x + 9 = 22 \] 3. **Rewrite the left side of the equation as a squared binomial:** \[ (x - 3)^2 = 22 \] 4. **Solve for \( x \):** Take the square root of both sides of the equation: \[ x - 3 = \pm \sqrt{22} \] 5. **Isolate \( x \):** \[ x = 3 \pm \sqrt{22} \] Therefore, the solutions to the equation \( x^2 - 6x = 13 \) are: \[ x = 3 + \sqrt{22} \quad \text{or} \quad x = 3 - \sqrt{22} \] ### Final Answer: The solutions are \( x = 3 + \sqrt{22} \) and \( x = 3 - \sqrt{22} \).
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