Your Turn!

Choose the option that best answers the question.

Write the equations of the lines passing through [tex]\((4,-3)\)[/tex] that are parallel and perpendicular to the line whose equation is [tex]\(y=-\frac{1}{2}x+5\)[/tex]. Express each equation in slope-intercept form.

A. [tex]\(y=-\frac{1}{2}x-1\)[/tex] is parallel

B. [tex]\(y=-\frac{1}{2}x-5\)[/tex] is parallel, [tex]\(y=2x-11\)[/tex] is perpendicular

C. [tex]\(y=-\frac{1}{2}x-1\)[/tex] is parallel, [tex]\(y=-2x+5\)[/tex] is perpendicular



Answer :

To find the equations of the lines passing through the point [tex]\((4, -3)\)[/tex] that are parallel and perpendicular to the line given by [tex]\(y = -\frac{1}{2} x + 5\)[/tex], we follow these steps:

1. Identify the slope of the given line:
The given line has the equation [tex]\(y = -\frac{1}{2} x + 5\)[/tex]. The slope of this line is [tex]\(-\frac{1}{2}\)[/tex].

2. Equation of the parallel line:
Lines that are parallel share the same slope. Therefore, the parallel line must also have a slope of [tex]\(-\frac{1}{2}\)[/tex].

Using the point-slope form of a line, [tex]\(y - y_1 = m(x - x_1)\)[/tex], where [tex]\((x_1, y_1)\)[/tex] is the point [tex]\((4, -3)\)[/tex] and [tex]\(m\)[/tex] is the slope:
[tex]\[ y - (-3) = -\frac{1}{2}(x - 4) \][/tex]
Simplify to get it into slope-intercept form [tex]\(y = mx + c\)[/tex]:
[tex]\[ y + 3 = -\frac{1}{2}x + 2 \][/tex]
[tex]\[ y = -\frac{1}{2}x - 1 \][/tex]

Therefore, the equation of the parallel line is [tex]\(y = -\frac{1}{2} x - 1\)[/tex].

3. Equation of the perpendicular line:
Perpendicular lines have slopes that are negative reciprocals. Thus, the slope of the line perpendicular to the given line is:
[tex]\[ m_{\text{perpendicular}} = -\frac{1}{\left(-\frac{1}{2}\right)} = 2 \][/tex]

Again, using the point-slope form with the point [tex]\((4, -3)\)[/tex] and the slope [tex]\(2\)[/tex]:
[tex]\[ y - (-3) = 2(x - 4) \][/tex]
Simplify to get it into slope-intercept form [tex]\(y = mx + c\)[/tex]:
[tex]\[ y + 3 = 2x - 8 \][/tex]
[tex]\[ y = 2x - 11 \][/tex]

Therefore, the equation of the perpendicular line is [tex]\(y = 2 x - 11\)[/tex].

Considering the options provided:
a. [tex]\(y = -\frac{1}{2} x - 1\)[/tex] is parallel
b. [tex]\(y = -\frac{1}{2} x - 5\)[/tex] is parallel [tex]\(y = 2 x - 11\)[/tex] is perpendicular
c. [tex]\(y = -\frac{1}{2} x - 1\)[/tex] is parallel [tex]\(y = \frac{1}{2} x + 5\)[/tex] is perpendicular [tex]\(y = -2 x + 5\)[/tex] is perpendicular

From the derived equations:
- The equation of the parallel line is [tex]\(y = -\frac{1}{2} x - 1\)[/tex], which matches option a and part of option c.
- The equation of the perpendicular line is [tex]\(y = 2 x - 11\)[/tex], which matches option b.

Thus, the correct option that best answers the question is:
a. [tex]\(y = -\frac{1}{2} x - 1\)[/tex] is parallel