Question

Consider the line y=-7x-1 what is the slope of a line perpendicular to this one

Answer 1

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

`y = \stackrel{\stackrel{m}{\downarrow }}{-7}x-1\qquad \impliedby \begin{array}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}`

thus a line perpendicular to that slope will have a slope of

`\stackrel{~\hspace{5em}\textit{perpendicular lines have \underline{negative reciprocal} slopes}~\hspace{5em}} {\stackrel{slope}{\cfrac{-7}{1}} ~\hfill \stackrel{reciprocal}{\cfrac{1}{-7}} ~\hfill \stackrel{negative~reciprocal}{-\cfrac{1}{-7}\implies {\LARGE \begin{array}{llll} \cfrac{1}{7} \end{array}}}}`

Answer 2

1/7

Explanation:

y = -7x - 1 so slope is -7

The slopes of two perpendicular lines are negative reciprocals of each other

so negative reciprocal of -7 is 1/7