A city planner is rerouting traffic in order to work on a stretch of road. The equation of the path of the old route can be described as [tex]y=\frac{2}{5} x-4[/tex]. What should the equation of the new route be if it is to be perpendicular to the old route and will go through point [tex]\((P, Q)\)[/tex]?

A. [tex]y - Q = -\frac{5}{2}(x - P)[/tex]
B. [tex]y - Q = \frac{2}{5}(x - P)[/tex]
C. [tex]y - P = -\frac{5}{2}(x - Q)[/tex]
D. [tex]y - P = \frac{2}{5}(x - Q)[/tex]



Answer :

To determine the equation of the new route, we need to follow these steps:

1. Identify the slope of the old route: The old route is given by the equation [tex]\(y = \frac{2}{5} x - 4\)[/tex]. The slope of this line is the coefficient of [tex]\(x\)[/tex], which is [tex]\(\frac{2}{5}\)[/tex].

2. Find the slope of the new route: Since the new route is to be perpendicular to the old route, its slope will be the negative reciprocal of the old route's slope. The negative reciprocal of [tex]\(\frac{2}{5}\)[/tex] is [tex]\(-\frac{5}{2}\)[/tex].

3. Form the equation of the perpendicular line: The point-slope form of the equation of a line is [tex]\(y - Q = m(x - P)\)[/tex], where [tex]\(m\)[/tex] is the slope and [tex]\((P, Q)\)[/tex] is the given point through which the line passes.

4. Substitute the slope and point into the point-slope form: We substitute the slope [tex]\(-\frac{5}{2}\)[/tex] and the point [tex]\((P, Q)\)[/tex] into the equation. This gives us:
[tex]\[ y - Q = -\frac{5}{2}(x - P) \][/tex]

After these steps, the equation for the new route is:
[tex]\[ y - Q = -\frac{5}{2}(x - P) \][/tex]

Hence, the correct option is:
[tex]\[ \boxed{y - Q = -\frac{5}{2}(x - P)} \][/tex]
This corresponds to the choice [tex]\(1\)[/tex].