Question

if y varies directly as the square of x, and y=775 when x=25 find y whenx=20

Answer 1

\(\bf \begin{array}{cccllll}
\textit{something }&\textit{varies directly to }&\textit{something else}\\ \quad \\
\textit{something }&={\color{red}{ \textit{some value }}}&\textit{something else}\\ \quad \\
y&={\color{red}{ n}}&x&\implies y={\color{red}{ n}}x
\end{array}
\\ \quad \\
y=775\qquad x=25\implies 775={\color{red}{ n}}(25)\qquad \textit{solve for "n"}\)

once you find "n", plug it in your original equation
to find "y" when x = 20, well, just set x = 20 in the original equation

Answer 2

ahemm o.... the square... so anhow... \(\bf \begin{array}{cccllll}
\textit{something }&\textit{varies directly to }&\textit{something else}\\ \quad \\
\textit{something }&={\color{red}{ \textit{some value }}}&\textit{something else}\\ \quad \\
y&={\color{red}{ n}}&x&\implies y={\color{red}{ n}}x^2
\end{array}
\\ \quad \\
y=775\qquad x=25\implies 775={\color{red}{ n}}(25)^2\qquad \textit{solve for "n"}\)