Select the correct answer.

[tex]$\overleftrightarrow{AB}$[/tex] and [tex]$\overleftrightarrow{BC}$[/tex] form a right angle at point [tex]$B$[/tex]. If [tex]$A=(-3,-1)$[/tex] and [tex]$B=(4,4)$[/tex], what is the equation of [tex]$\overleftrightarrow{BC}$[/tex]?

A. [tex]$x + 3y = 16$[/tex]

B. [tex]$2x + y = 12$[/tex]

C. [tex]$-7x - 5y = -48$[/tex]

D. [tex]$7x - 5y = 48$[/tex]



Answer :

To find the equation of the line [tex]\(\overleftrightarrow{BC}\)[/tex] that forms a right angle with the line [tex]\(\overleftrightarrow{AB}\)[/tex] at point [tex]\(B\)[/tex], we need to follow these steps:

1. Find the slope of [tex]\(\overleftrightarrow{AB}\)[/tex]:
Given the points [tex]\(A = (-3, -1)\)[/tex] and [tex]\(B = (4, 4)\)[/tex], we use the formula for the slope [tex]\(m\)[/tex]:

[tex]\[ m_{AB} = \frac{y_2 - y_1}{x_2 - x_1} \][/tex]

Substituting the given points [tex]\(A\)[/tex] and [tex]\(B\)[/tex]:

[tex]\[ m_{AB} = \frac{4 - (-1)}{4 - (-3)} = \frac{4 + 1}{4 + 3} = \frac{5}{7} \][/tex]

2. Determine the slope of [tex]\(\overleftrightarrow{BC}\)[/tex]:
Since [tex]\(\overleftrightarrow{BC}\)[/tex] is perpendicular to [tex]\(\overleftrightarrow{AB}\)[/tex], its slope [tex]\(m_{BC}\)[/tex] will be the negative reciprocal of [tex]\(m_{AB}\)[/tex]:

[tex]\[ m_{BC} = -\frac{1}{m_{AB}} = -\frac{1}{\frac{5}{7}} = -\frac{7}{5} \][/tex]

3. Use point-slope form of the line equation:
We know the slope of [tex]\(\overleftrightarrow{BC}\)[/tex] and it passes through [tex]\(B = (4, 4)\)[/tex]. The point-slope form of the line equation is:

[tex]\[ y - y_1 = m(x - x_1) \][/tex]

Substituting [tex]\(m = -\frac{7}{5}\)[/tex] and the coordinates of point [tex]\(B\)[/tex]:

[tex]\[ y - 4 = -\frac{7}{5}(x - 4) \][/tex]

4. Convert to general form [tex]\(Ax + By = C\)[/tex]:
Simplify and rearrange the equation to standard form:

[tex]\[ y - 4 = -\frac{7}{5}(x - 4) \][/tex]

Multiply both sides by 5 to eliminate the fraction:

[tex]\[ 5(y - 4) = -7(x - 4) \][/tex]

Distribute and simplify:

[tex]\[ 5y - 20 = -7x + 28 \][/tex]

Bring all terms to one side to achieve the general form [tex]\(Ax + By = C\)[/tex]:

[tex]\[ 7x - 5y = 48 \][/tex]

Thus, the equation of the line [tex]\(\overleftrightarrow{BC}\)[/tex] is:

[tex]\[ 7x - 5y = 48 \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{D \, \text{ 7x - 5y = 48}} \][/tex]