Anotherway to say this theoremis, if the slopesof two lines multiplyto then the two lines are perpen-
dicular.
The oppositereciprocalcan be foundin two steps.First,find the reciprocalof the givenslope.If the slope
is a fraction,you can simplyswitchthe numbersin the numeratorand denominator. If the valueis not a
fraction,you can makeit into one by puttinga 1 in the numeratorand the givenvaluein the denominator.
The reciprocalof is and the reciprocalof 5 is. The secondstep is to find the oppositeof the given
number. If the valueis positive,makeit negative.If the valueis negative,makeit positive.The oppositere-
ciprocalof is and the oppositereciprocalof 5 is.
Example 6
Whichof the followingcouldrepresentthe slopeof a line perpendicularto the one shownbelow?A.
B.
C.
D.
Sinceyou are lookingfor the slopeof a perpendicularline, it will be the oppositereciprocalof the slopeof
the line in the diagram.First identifythe slopeof the line given,then find the oppositereciprocal,and finally
selectthe answerwith that value.You can use the slopeformulato find the originalslope.Pick two points
on the line. For example,(-3,-2)and (4,3).