Question

Write function rule and find k.

1) z varies jointly with x and y, and
when x=2 and y=3, z=72

Answer 1

z = 12xy

Explanation:

Given z varies jointly with x and y then the equation relating them is

z = kxy ← k is the constant of variation

To find k use the condition when x = 2 and y = 3, z = 72, that is

72 = k × 2 × 3 = 6k ( divide both sides by 6 )

12 = k , then

z = 12xy ← equation of variation