Find the variation equation for the variation statement.
-$z$ varies jointly as $y$ and the cube of $x ; z = 960$ when $x = 4$ and $y = - 5$
A) $y = 3 x ^ { 3 } y$
B) $y = - 3 x ^ { 3 } y$
C) $y = - 3 x y ^ { 3 }$
D) $y = 3 x y ^ { 3 }$

Question

Quizplus · Accepted Answer

The variation equation for $z$ varies jointly as $y$ and the cube of $x$ is $z = kxy^3$. Substituting $z = 960$, $x = 4$, and $y = -5$ into the equation gives $960 = k(4)(-5)^3$. Solving for $k$ gives $k = -3$, so the correct equation is $z = -3x^3y$, which matches choice B.

Find the Variation Equation for the Variation Statement zzz Varies Jointly As

Find the Variation Equation for the Variation Statement $z$ Varies Jointly As