3. If AB = 8x + 5, CB = 10x - 1, and BD AC, 1 solve for x.

Elementary Geometry For College Students, 7e
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ISBN:9781337614085
Author:Alexander, Daniel C.; Koeberlein, Geralyn M.
Publisher:Alexander, Daniel C.; Koeberlein, Geralyn M.
ChapterP: Preliminary Concepts
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### Solving for \( x \) in an Isosceles Triangle

**Problem Statement:**
Given that \( AB = 8x + 5 \), \( CB = 10x - 1 \), and \( BD \perp AC \), solve for \( x \). 

A triangle \( ABC \) is illustrated where \( BD \) is the altitude from \( B \) to \( AC \), making $\angle BDA$ and $\angle BDC$ right angles. 

**Steps to Solve:**

1. **Understanding the Isosceles Triangle:**
   Since \( AB \) and \( CB \) are given by two distinct expressions but the problem involves isosceles properties (indicated by mid-perpendicular lines indicating equality), we can set \( AB \) equal to \( CB \).

2. **Set the expressions equal:**
   \[
   8x + 5 = 10x - 1
   \]

3. **Isolate \( x \):**
   \[
   10x - 8x = 5 + 1
   \]
   \[
   2x = 6
   \]
   \[
   x = 3
   \]

4. **Verify the Value:**
   - Plug \( x = 3 \) back into the expressions to ensure both sides are equal:
     - For \( AB \): \( 8(3) + 5 = 24 + 5 = 29 \)
     - For \( CB \): \( 10(3) - 1 = 30 - 1 = 29 \)

Both sides equal \( 29 \), confirming the solution is correct. 

5. **Conclusion:**
   Therefore, the value of \( x \) is:
   \[
   x = 3
   \]

**Visual Explanation:**

- **Diagram Description:**
   The diagram shows triangle \( ABC \) with \( BD \) as the altitude. The marks on \( AB \) and \( CB \) indicate these two sides are equal in length (as it is an isosceles triangle with \( AB = CB \)).

   
By following the steps above, students can solve for the variable \( x \) in isosceles triangles given similar length expressions. The diagram reinforces the understanding of altitude and properties specific to isosceles triangles.
Transcribed Image Text:### Solving for \( x \) in an Isosceles Triangle **Problem Statement:** Given that \( AB = 8x + 5 \), \( CB = 10x - 1 \), and \( BD \perp AC \), solve for \( x \). A triangle \( ABC \) is illustrated where \( BD \) is the altitude from \( B \) to \( AC \), making $\angle BDA$ and $\angle BDC$ right angles. **Steps to Solve:** 1. **Understanding the Isosceles Triangle:** Since \( AB \) and \( CB \) are given by two distinct expressions but the problem involves isosceles properties (indicated by mid-perpendicular lines indicating equality), we can set \( AB \) equal to \( CB \). 2. **Set the expressions equal:** \[ 8x + 5 = 10x - 1 \] 3. **Isolate \( x \):** \[ 10x - 8x = 5 + 1 \] \[ 2x = 6 \] \[ x = 3 \] 4. **Verify the Value:** - Plug \( x = 3 \) back into the expressions to ensure both sides are equal: - For \( AB \): \( 8(3) + 5 = 24 + 5 = 29 \) - For \( CB \): \( 10(3) - 1 = 30 - 1 = 29 \) Both sides equal \( 29 \), confirming the solution is correct. 5. **Conclusion:** Therefore, the value of \( x \) is: \[ x = 3 \] **Visual Explanation:** - **Diagram Description:** The diagram shows triangle \( ABC \) with \( BD \) as the altitude. The marks on \( AB \) and \( CB \) indicate these two sides are equal in length (as it is an isosceles triangle with \( AB = CB \)). By following the steps above, students can solve for the variable \( x \) in isosceles triangles given similar length expressions. The diagram reinforces the understanding of altitude and properties specific to isosceles triangles.
### Example Question from Geometry: Understanding Isosceles Triangles

#### Question:
In the figure given, triangle ABC is isosceles with \( AB = AC \). Point D is the midpoint of the base BC, and the segment AD is perpendicular to BC.

Given that:

- Triangle ABC is an isosceles triangle with AB = AC
- Point D is the midpoint of BC
- Segment AD is perpendicular to BC

What is the ratio of the lengths \( \frac{AD}{DB} \) (denoted as \( x \))?

#### Choose the correct answer from the options below:
- \( x = 2 \)
- \( x = 1.5 \)
- \( x = 3 \)
- \( x = 1 \)

#### Explanation:
In an isosceles triangle, the altitude from the vertex angle bisects the base into two equal parts. Since \( D \) is the midpoint of \( BC \), and \( AD \) is perpendicular to \( BC \), the triangles \( ABD \) and \( ACD \) are congruent.

Let's explore the possible values for \( x \) based on the information given in the problem. The correct ratio can be determined using properties of isosceles triangles and perpendicular bisectors.

### Answer:
Use the properties of the isosceles triangle to solve this problem. The correct ratio \( x \) can be deduced by understanding the nature of the triangles and applying the appropriate theorems or formulas.

---

This explanation ensures that students understand the question and can apply geometric properties to find the right answer.
Transcribed Image Text:### Example Question from Geometry: Understanding Isosceles Triangles #### Question: In the figure given, triangle ABC is isosceles with \( AB = AC \). Point D is the midpoint of the base BC, and the segment AD is perpendicular to BC. Given that: - Triangle ABC is an isosceles triangle with AB = AC - Point D is the midpoint of BC - Segment AD is perpendicular to BC What is the ratio of the lengths \( \frac{AD}{DB} \) (denoted as \( x \))? #### Choose the correct answer from the options below: - \( x = 2 \) - \( x = 1.5 \) - \( x = 3 \) - \( x = 1 \) #### Explanation: In an isosceles triangle, the altitude from the vertex angle bisects the base into two equal parts. Since \( D \) is the midpoint of \( BC \), and \( AD \) is perpendicular to \( BC \), the triangles \( ABD \) and \( ACD \) are congruent. Let's explore the possible values for \( x \) based on the information given in the problem. The correct ratio can be determined using properties of isosceles triangles and perpendicular bisectors. ### Answer: Use the properties of the isosceles triangle to solve this problem. The correct ratio \( x \) can be deduced by understanding the nature of the triangles and applying the appropriate theorems or formulas. --- This explanation ensures that students understand the question and can apply geometric properties to find the right answer.
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