A software designer is mapping the streets for a new racing game. All of the streets are depicted as either perpendicular or parallel lines. The equation of the lane passing through points \(A\) and \(B\) is \( -7x + 3y = -21.5 \). What is the equation of the central street \(PQ\)?

A. \(-3x + 4y = 3\)

B. \(3x + 7y = 63\)

C. \(2x + y = 20\)

D. [tex]\(7x + 3y = 70\)[/tex]



Answer :

To determine the equation of the central street \( PQ \), which is perpendicular to the lane passing through points \( A \) and \( B \), we need to go through a series of steps. Let's begin.

### Step 1: Identify the Slope of the Given Lane

The equation of the lane passing through \( A \) and \( B \) is given by:
[tex]\[ -7x + 3y = -21.5 \][/tex]

We need to determine the slope of this line. First, we convert this equation to the slope-intercept form, \( y = mx + b \), where \( m \) is the slope.

Let's isolate \( y \):

[tex]\[ 3y = 7x - 21.5 \][/tex]

[tex]\[ y = \frac{7}{3}x - \frac{21.5}{3} \][/tex]

From this equation, we can see that the slope \( m \) of the line \( AB \) is:

[tex]\[ m = \frac{7}{3} \][/tex]

### Step 2: Determine the Slope of the Perpendicular Line

The central street \( PQ \) should be perpendicular to \( AB \). The slope of a line perpendicular to another line is the negative reciprocal of the slope of the original line.

The slope of \( AB \) is \( \frac{7}{3} \). Therefore, the slope of \( PQ \) (perpendicular to \( AB \)) is:

[tex]\[ -\frac{1}{\frac{7}{3}} = -\frac{3}{7} \][/tex]

### Step 3: Form the Equation of the Perpendicular Line

Now we need the equation of the line with the slope \( -\frac{3}{7} \). We can start by using the slope-intercept form \( y = mx + b \), then convert it to the general form \( Ax + By = C \).

The line equation with slope \( -\frac{3}{7} \):

[tex]\[ y = -\frac{3}{7}x + b \][/tex]

Rearrange the equation to the form \( Ax + By = C \):

[tex]\[ 7y = -3x + 7b \][/tex]

[tex]\[ 3x + 7y = 7b \][/tex]

This is the general form of the equation of the central street \( PQ \).

### Step 4: Identify the Correct Option

To match this form with the provided options, compare:

[tex]\[ 3x + 7y = C \][/tex]

The constant \( 7b \) in our general form represents the value on the right-hand side. Therefore, the correct equation from the given choices that fits this form is:

[tex]\[ 3x + 7y = 63 \][/tex]

Thus, the correct equation for the central street \( PQ \) is:

B. [tex]\( 3x + 7y = 63 \)[/tex]

Other Questions