Question

The points R(4, t), S(3, 8) and T(1, 2) lie on a same straight line. Find the value of t.​

Answer 1

well, we know that R, S and T are on the same straight line, hmmmm wait a second!! that means that the slope for RS must be the same as the slope for ST, heck, what's the slope for ST anyway?

`S(\stackrel{x_1}{3}~,~\stackrel{y_1}{8})\qquad T(\stackrel{x_2}{1}~,~\stackrel{y_2}{2}) ~\hfill \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{2}-\stackrel{y1}{8}}}{\underset{run} {\underset{x_2}{1}-\underset{x_1}{3}}} \implies \cfrac{ -6 }{ -2 } \implies 3`

ahha!! that means that the slope for RS is really 3, hmmmm

`R(\stackrel{x_1}{4}~,~\stackrel{y_1}{t})\qquad S(\stackrel{x_2}{3}~,~\stackrel{y_2}{8}) ~\hfill \stackrel{slope}{m}\implies \cfrac{\stackrel{rise} {\stackrel{y_2}{8}-\stackrel{y1}{t}}}{\underset{run} {\underset{x_2}{3}-\underset{x_1}{4}}} ~~ = ~~\stackrel{\textit{\LARGE m}}{3} \\\\\\ \cfrac{8-t}{-1}=3\implies 8-t=-3\implies 11-t=0\implies 11=t`