Question

hi guys, i missed an entire lesson on direct and indirect variation. help me out?
tell whether x and y show direct/ indirect variation or neither.
4. xy= 1/4
5. x/y=5
6.y=x-3
7. x=7/y
8. y/x=12
9. 1/2xy=9
10. y=1/x
11. 2x+y=4

Tell whether x varies jointly with y and z
1. x=15yz
2. x/z= 0.5y
3. xy=4z

Answer 1

solve each of them for "y"
then once is solve for "y", look at them :)

keeping in mind that \(\begin{array}{cccllll}
\textit{something }&\textit{varies directly to }&\textit{something else}\\ \quad \\
\textit{something }&={\color{red}{ \textit{some value }}}&\textit{something else}\\ \quad \\
y&={\color{red}{ n}}&x&\implies y={\color{red}{ n}}x
\end{array}\\ \quad \\

--------------------------------\\


\begin{array}{cccllll}
\textit{something }&\textit{varies inversely to }&\textit{something else}\\ \quad \\
\textit{something }&=\cfrac{{\color{red}{ \textit{some value }}}}{\textit{something else}}\\ \quad \\
y&=\cfrac{{\color{red}{ n}}}{x}
&&\implies y=\cfrac{{\color{red}{ n}}}{x}
\end{array}\)

Answer 2

something varies INDIRECTLY = something varies INVERSELY

indirect variation => inverse variation

Answer 3

@jdoe0001 can you give me an example please?