Two variables and are inversely proportional if their product is constant. That means you always get the same answer when you multiply and together.
Two variables and are inversely proportional if
where is a constant.
Saying that is the same as saying that :
This graph shows , that is, . The graph is inversely proportional, so for all points on the graph, if you multiply the -coordinate by the -coordinate, the answer is .
Is the graph inversely proportional?
You can find that out by doing a few conversions:
You’ve found that , so the graph is inversely proportional.
You have been given the following points:
-values 1 2 3 4 5 -values 20 10 7 5 4
Do the points follow an inversely proportional function?
From the theory, you know that if multiply the -value by the -value and the answer is the same for all points, then the points follow an inversely proportional function. You check the points from the table:
Because one of the answers is not the same as the others, they do not follow an inversely proportional function.