In the [tex]\(xy\)[/tex]-plane, line [tex]\(l\)[/tex] passes through the origin and is perpendicular to the line with equation [tex]\(5x - 2y = 8\)[/tex]. Which of the following could be an equation of line [tex]\(l\)[/tex]?

A. [tex]\(2x + 5y = 0\)[/tex]
B. [tex]\(5x + 2y = 0\)[/tex]
C. [tex]\(2x - 5y = 0\)[/tex]
D. [tex]\(-2x + 5y = 0\)[/tex]



Answer :

To find an equation of a line that passes through the origin and is perpendicular to the line given by the equation [tex]\(5x - 2y = 8\)[/tex], follow these steps:

1. Determine the slope of the given line:

The given line’s equation is [tex]\(5x - 2y = 8\)[/tex].

First, we'll rewrite this equation in the slope-intercept form [tex]\(y = mx + b\)[/tex], where [tex]\(m\)[/tex] is the slope.

[tex]\[ 5x - 2y = 8 \][/tex]

Solving for [tex]\(y\)[/tex], we get:

[tex]\[ -2y = -5x + 8 \][/tex]

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

Therefore, the slope ([tex]\(m_1\)[/tex]) of the line [tex]\(5x - 2y = 8\)[/tex] is [tex]\(\frac{5}{2}\)[/tex].

2. Find the slope of the perpendicular line:

For a line to be perpendicular to another, its slope ([tex]\(m_2\)[/tex]) should be the negative reciprocal of the slope of the original line.

The negative reciprocal of [tex]\(\frac{5}{2}\)[/tex] is:

[tex]\[ m_2 = -\frac{1}{\frac{5}{2}} = -\frac{2}{5} \][/tex]

3. Write the equation of the perpendicular line:

The line we are looking for passes through the origin, which means it has a y-intercept [tex]\(b = 0\)[/tex] when written in slope-intercept form [tex]\(y = mx + b\)[/tex].

With the slope [tex]\(m_2 = -\frac{2}{5}\)[/tex] and [tex]\(b = 0\)[/tex], the equation of the line becomes:

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

4. Convert the equation to standard form:

To write this equation in standard form [tex]\(Ax + By = C\)[/tex], we rearrange it:

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

Multiply both sides by 5 to eliminate the fraction:

[tex]\[ 5y = -2x \][/tex]

Rearrange to get:

[tex]\[ 2x + 5y = 0 \][/tex]

Thus, the equation of the line that passes through the origin and is perpendicular to the line [tex]\(5x - 2y = 8\)[/tex] is:

[tex]\[ 2x + 5y = 0 \][/tex]