Question

Line A is perpendicular to line B. The slope of line A is -1/9 what is the slope of line b?

Answer 1

The slope of the line is 9

Answer 2

$\bf \stackrel{\textit{perpendicular lines have \underline{negative reciprocal} slopes}} {\stackrel{slope}{-\cfrac{1}{9}}\qquad \qquad \qquad \stackrel{reciprocal}{-\cfrac{9}{1}}\qquad \stackrel{negative~reciprocal}{+\cfrac{9}{1}}\implies 9}$