word problem

Question

z
varies jointly with
y
and the square of
x. If z=−84 when y=-7
and
x=−2, find z when x=−3 and y=-6
 

Answer 1

z = kyx², k = constant

 

Find k from the given values.

 

-84 = k(-7)(-2)²

-84 = -28k

k = 3

 

For y = -6 and x = -3,

z = kyx² = 3(-6)(-3)² = -162