Question

Inverse proportion- please can someone help me with this question? thanks!

Answer 1

`\qquad \qquad \textit{inverse proportional variation} \\\\ \textit{\underline{y} varies inversely with \underline{x}} ~\hspace{6em} \stackrel{\textit{constant of variation}}{y=\cfrac{\stackrel{\downarrow }{k}}{x}~\hfill } \\\\ \textit{\underline{x} varies inversely with }\underline{z^5} ~\hspace{5.5em} \stackrel{\textit{constant of variation}}{x=\cfrac{\stackrel{\downarrow }{k}}{z^5}~\hfill } \\\\[-0.35em] ~\dotfill`

`\stackrel{\textit{S varies inversely with }F^2}{S = \cfrac{k}{F^2}}\hspace{5em}\textit{we also know that} \begin{cases} F=8\\ S=125 \end{cases} \\\\\\ 125=\cfrac{k}{8}\implies (125)(8)=k\implies 1000=k~\hfill \boxed{S=\cfrac{1000}{F^2}} \\\\\\ \textit{when F=4, what is`