Question

Dont know the answer to last question

Answer 1

keeping in mind that parallel lines have exactly the same slope, let's check for the slope of the line AB.... hmmm wait a second!!!, you found it already, well, we know AB has a slope of -1/3.

so we're really looking for the equation of a line whose slope is -1/3 and that it passes through (0 , -5)

`(\stackrel{x_1}{0}~,~\stackrel{y_1}{-5})\hspace{10em} \stackrel{slope}{m} ~=~ - \cfrac{1}{3} \\\\\\ \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}{(-5)}=\stackrel{m}{- \cfrac{1}{3}}(x-\stackrel{x_1}{0}) \implies y +5= -\cfrac{1}{3} (x -0) \\\\\\ y+5=-\cfrac{1}{3}x\implies {\Large \begin{array}{llll} y=-\cfrac{1}{3}x-5 \end{array}}`