ALGEBRA 2
Name:_________________________________ Date:_____________
Warm-Up: Direct Variation
1) x and y vary directly. If y = -12 when x = 4…
a) Write an equation that relates x and y.
b) Find y when x = 5.
2) x and y vary directly. If y = 3 when x = 18…
a) Write an equation that relates x and y.
b) Find y when x = 7.
____________________________________________________________
Inverse Variation
 y varies inversely with x if
o k is called the _________________ of _______________________.
o Two quantities vary inversely if as one quantity increases, the other quantity decreases.
o Another phrase for “Inverse Variation” is ______________________________________ or
______________________________________.
o An example formula is ________________
- Density and volume vary indirectly, which means as volume increases, density decreases.
Examples:
3) y varies inversely with x. If y = -12 when x = 4…
a) Write an equation that relates x and y.
b) Find y when x = 16.
4) y varies inversely with x. If y = 3 when x = 6…
a) Write an equation that relates x and y.
b) Find y when x = -4.
Practice:
5) y varies inversely with x. If y = 6 when x = -2…
a) Write an equation that relates x and y.
b) Find y when x = -7.
6) y varies inversely with x. If y = -4 when x = -3…
a) Write an equation that relates x and y.
b) Find y when x = 2.
Application Example:
The time it takes to paint a house varies inversely with the number of painters that are helping. It takes 1 painter a total
of 20 days to paint an entire house. Write an equation to represent how long (y) it would take x painters to paint the
same house. Graph your equation. Then, determine how long it would take 8 painters to paint that same house.
Practice from the Textbook: