Question 66 of 480
3y = 4x - 1 and Ky = x + 3 are equations of two straight lines. If the two lines are perpendicular to each other, find K.
- A. -4/3
- B. -3/4
- C. 3/4
- D. 4/3
Correct Answer:
A
Explanation
To determine the value of \( K \) such that the lines represented by the equations \( 3y = 4x - 1 \) and \( Ky = x + 3 \) are perpendicular, we need to follow these steps:
### Step 1: Convert the equations to slope-intercept form
The slope-intercept form of a line is given by the equation \( y = mx + b \), where \( m \) is the slope of the line.
**For the first equation:**
\[ 3y = 4x - 1 \]
To convert this to slope-intercept form, divide every term by 3:
\[ y = \frac{4}{3}x - \frac{1}{3} \]
From this, we can see that the slope \( m_1 \) of the first line is:
\[ m_1 = \frac{4}{3} \]
**For the second equation:**
\[ Ky = x + 3 \]
To convert this to slope-intercept form, divide every term by \( K \):
\[ y = \frac{1}{K}x + \frac{3}{K} \]
From this, we can see that the slope \( m_2 \) of the second line is:
\[ m_2 = \frac{1}{K} \]
### Step 2: Use the condition for perpendicular lines
Two lines are perpendicular if the product of their slopes is equal to -1. Therefore, we can set up the following equation:
\[ m_1 \cdot m_2 = -1 \]
Substituting the slopes we found:
\[ \left(\frac{4}{3}\right) \cdot \left(\frac{1}{K}\right) = -1 \]
### Step 3: Solve for \( K \)
Now, we can solve for \( K \):
\[ \frac{4}{3K} = -1 \]
To eliminate the fraction, multiply both sides by \( 3K \):
\[ 4 = -3K \]
Now, divide both sides by -3:
\[ K = -\frac{4}{3} \]
### Conclusion
Thus, the value of \( K \) that makes the two lines perpendicular is:
**A. -4/3**
### Explanation of Other Options
- **B. -3/4**: This value does not satisfy the condition for perpendicularity since substituting \( K = -\frac{3}{4} \) into the slope equation would not yield a product of -1.
- **C. 3/4**: This value would yield a positive product of slopes, which cannot satisfy the perpendicular condition.
- **D. 4/3**: This would also yield a positive product of slopes, which is not suitable for perpendicular lines.
### Revision Summary
- Convert line equations to slope-intercept form to identify slopes.
- Use the condition \( m_1 \cdot m_2 = -1 \) for perpendicular lines.
- Solve for \( K \) to find the required value.
- The correct answer is \( K = -\frac{4}{3} \).