Question

Which equation represents y as a function of x?

Answer 1

to get the equation of any straight line, we simply need two points off of it, let's use those two in the picture below

`(\stackrel{x_1}{40}~,~\stackrel{y_1}{30})\qquad (\stackrel{x_2}{100}~,~\stackrel{y_2}{75}) ~\hfill \stackrel{slope}{m}\implies \cfrac{\stackrel{\textit{\large rise}} {\stackrel{y_2}{75}-\stackrel{y1}{30}}}{\underset{\textit{\large run}} {\underset{x_2}{100}-\underset{x_1}{40}}} \implies \cfrac{ 45 }{ 60 } \implies \cfrac{ 3 }{ 4 }`

`\begin{array}ll \cline{1-1} \textit{point-slope form}\\ \cline{1-1} \\ y-y_1=m(x-x_1) \\\\ \cline{1-1} \end{array}\implies y-\stackrel{y_1}{30}=\stackrel{m}{ \cfrac{ 3 }{ 4 }}(x-\stackrel{x_1}{40}) \\\\\\ y-30=\cfrac{ 3 }{ 4 }x-30\implies {\Large \begin{array}{llll} y=\cfrac{ 3 }{ 4 }x \end{array}}`