Opposite means add a negative sign in front of it.
The opposite of 6 is -6,
7 --> -7,
-10 --> 10.
Reciprocal means flip it.
Reciprocal of 6 is 1/6
of 7 is 1/7
of -10 is -1/10
Opposite reciprocal means add a negative sign AND flip it.
6 --> -1/6
7 ---> -1/7
-10 --> 1/10
In geometry, perpendicular lines on a graph have opposite reciprocal slopes.