# Chapter 7 - Functions and Graphs - 7.5 Formulas, Applications, and Variation - 7.5 Exercise Set - Page 488: 73

$\color{blue}{y=\frac{3}{2}xz}$

#### Work Step by Step

RECALL: When $y$ varies jointly as $x$ and $z$, the variation is represented by the equation $y=kxz$ where $k$ is the constant of variation. $y$ varies jointly as $x$ and $z$ so the equation of the variation is $y=kxz$ with $k$=constant of variation. To find the value of $k$, substitute the given values into $y=kxz$ to obtain: $$y=kxz \\105=k(14)(5) \\105=70k \\\frac{105}{70}=\frac{70k}{70} \\\frac{3}{2}=k$$ Thus, the equation of the variation is: $\color{blue}{y=\frac{3}{2}xz}$.

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