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 :

Certainly! Let's solve the problem step-by-step to find the equation of line [tex]\(\overleftrightarrow{B C}\)[/tex].

1. Identify the given points:
- Point [tex]\(A\)[/tex] is [tex]\((-3, -1)\)[/tex].
- Point [tex]\(B\)[/tex] is [tex]\((4, 4)\)[/tex].

2. Find the slope of line [tex]\(\overleftrightarrow{A B}\)[/tex]:
- The formula for the slope [tex]\(m\)[/tex] between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is [tex]\( m = \frac{y_2 - y_1}{x_2 - x_1} \)[/tex].
- Substituting the coordinates of 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]

3. Determine the slope of line [tex]\(\overleftrightarrow{B C}\)[/tex]:
- Lines [tex]\(\overleftrightarrow{A B}\)[/tex] and [tex]\(\overleftrightarrow{B C}\)[/tex] form a right angle at point [tex]\(B\)[/tex].
- Therefore, the slopes of these lines are negative reciprocals of each other.
- Hence, the slope [tex]\(m_{BC}\)[/tex] of line [tex]\(\overleftrightarrow{B C}\)[/tex] is:
[tex]\[ m_{BC} = -\frac{1}{m_{AB}} = -\frac{1}{\frac{5}{7}} = -\frac{7}{5} \][/tex]

4. Form the equation of the line [tex]\(\overleftrightarrow{B C}\)[/tex] using point-slope form:
- The point-slope form of a line's equation is given by:
[tex]\[ y - y_1 = m(x - x_1) \][/tex]
- Substituting the slope [tex]\(m_{BC} = -\frac{7}{5}\)[/tex] and the coordinates of point [tex]\(B\)[/tex] [tex]\((4, 4)\)[/tex]:
[tex]\[ y - 4 = -\frac{7}{5}(x - 4) \][/tex]

5. Simplify the equation to general form:
- Expand the equation:
[tex]\[ y - 4 = -\frac{7}{5}x + \frac{28}{5} \][/tex]
- Multiply every term by 5 to eliminate the fraction:
[tex]\[ 5(y - 4) = 5 \left( -\frac{7}{5}x + \frac{28}{5} \right) \][/tex]
[tex]\[ 5y - 20 = -7x + 28 \][/tex]
[tex]\[ 7x + 5y = 48 \][/tex]

Therefore, the equation of line [tex]\(\overleftrightarrow{B C}\)[/tex] is:

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

The correct answer is:

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

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