Consider the line y=7x-5. Find the equation of the line that is perpendicular to this line and passes through the point (-8, -6). Find the equation of the this line that is parallel to the point (-8, -6).

Respuesta :

Answer:

Equation is y = -1/7x - 50/7   or    y = -1/7x - 7 1/7

Step-by-step explanation:

Perpendicular lines slopes are negative reciprocals of each other.

y = 7x - 5  This equation slope = 7 because the slope is the coefficient of the x-term.  

The line that is perpendicular will have a slope of -1/7 ( the negative reciprocal of 7)

Next to find the value of "b" using y = mx + b and slope of -1/7 and point (-8, -6).

y = mx + b

-6 =  -1/7(-8) + b

-6 = 8/7 + b

-6 - 8/7 = b

-50/7 = b

Equation is y = -1/7x - 50/7  or    y = -1/7x - 7 1/7

keeping in mind that perpendicular lines have negative reciprocal slopes, let's check for the slope of the equation above

[tex]\begin{array}{|c|ll}\cline{1-1}slope-intercept~form\\\cline{1-1}\\y=\underset{y-intercept}{\stackrel{slope\qquad }{\stackrel{\downarrow }{m}x+\underset{\uparrow }{b}}}\\\\\cline{1-1}\end{array}~\hspace{10em} y = \stackrel{\stackrel{m}{\downarrow }}{7}x - 5\\\\[-0.35em]~\dotfill[/tex]

[tex]\stackrel{\textit{perpendicular lines have \underline{negative reciprocal} slopes}}{\stackrel{slope}{7\to \cfrac{7}{1}}\qquad \qquad \qquad \stackrel{reciprocal}{\cfrac{1}{7}}\qquad \stackrel{negative~reciprocal}{-\cfrac{1}{7}}}[/tex]

so we know that it has a slope of -1/7 and passed through (-8,-6)

[tex](\stackrel{x_1}{-8}~,~\stackrel{y_1}{-6}) ~\hspace{10em} \stackrel{slope}{m}\implies - \cfrac{1}{7} \\\\\\ \begin{array}{|c|ll} \cline{1-1} \textit{point-slope form}\\ \cline{1-1} \\ y-y_1=m(x-x_1) \\\\ \cline{1-1} \end{array}\implies y-\stackrel{y_1}{(-6)}=\stackrel{m}{-\cfrac{1}{7}}[x-\stackrel{x_1}{(-8)}] \implies y+6=-\cfrac{1}{7}(x+8) \\\\\\ y+6=-\cfrac{1}{7}x-\cfrac{8}{7}\implies y=-\cfrac{1}{7}x-\cfrac{8}{7}-6\implies ~\hfill y=-\cfrac{1}{7}x-\cfrac{50}{7}[/tex]