Which equation represents a line that is perpendicular to the line passing through [tex](-4,7)[/tex] and [tex](1,3)[/tex]?

A. [tex]y = \frac{4}{5}x - 3[/tex]

B. [tex]y = -\frac{4}{5}x + 6[/tex]

C. [tex]y = \frac{5}{4}x + 8[/tex]

D. [tex]y = -\frac{5}{4}x - 2[/tex]



Answer :

To find which equation represents a line that is perpendicular to the line passing through the points [tex]\((-4, 7)\)[/tex] and [tex]\( (1, 3) \)[/tex], we need to follow these steps:

1. Calculate the slope of the line passing through the points [tex]\((-4, 7)\)[/tex] and [tex]\( (1, 3) \)[/tex].

The formula for the slope [tex]\(m\)[/tex] of a line passing through 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]

Applying the given points:
[tex]\[ m = \frac{3 - 7}{1 - (-4)} = \frac{-4}{1 + 4} = \frac{-4}{5} \][/tex]

So, the slope of the line passing through these points is [tex]\( -\frac{4}{5} \)[/tex].

2. Determine the slope of the line that is perpendicular.

The slope of a line that is perpendicular to another line is the negative reciprocal of the original slope. For a slope [tex]\(m\)[/tex], the slope of the perpendicular line is [tex]\(-\frac{1}{m}\)[/tex].

Given the original slope is [tex]\(-\frac{4}{5}\)[/tex], the slope of the perpendicular line is:
[tex]\[ -\frac{1}{\left(-\frac{4}{5}\right)} = \frac{5}{4} \][/tex]

3. Match the calculated perpendicular slope with the slopes given in the options.

Let's analyze the provided options:
- Option A: [tex]\( y = \frac{4}{5}x - 3 \)[/tex] has a slope of [tex]\( \frac{4}{5} \)[/tex]
- Option B: [tex]\( y = -\frac{4}{5}x + 6 \)[/tex] has a slope of [tex]\(-\frac{4}{5} \)[/tex]
- Option C: [tex]\( y = \frac{5}{4}x + 8 \)[/tex] has a slope of [tex]\( \frac{5}{4} \)[/tex]
- Option D: [tex]\( y = -\frac{5}{4}x - 2 \)[/tex] has a slope of [tex]\(-\frac{5}{4} \)[/tex]

Out of these options, only Option C has the slope [tex]\( \frac{5}{4} \)[/tex], which matches the slope of the perpendicular line we calculated.

Therefore, the equation that represents a line perpendicular to the line passing through [tex]\((-4, 7)\)[/tex] and [tex]\((1, 3)\)[/tex] is:
[tex]\[ \boxed{y = \frac{5}{4} x + 8} \][/tex]