Question

line q has an eqaution of y= -10/9x +2. line r includes the point (9, -3) and is parallel to line q. What is the eqaution of line r.​

Answer 1

keeping in mind that parallel lines have exactly the same slope, let's check for the slope of line Q

`y=\stackrel{\stackrel{m}{\downarrow }}{-\cfrac{10}{9}}x+2\qquad \impliedby \qquad \begin{array}c \cline{1-1} slope-intercept~form\\ \cline{1-1} \\ y=\underset{y-intercept}{\stackrel{slope\qquad }{\stackrel{\downarrow }{m}x+\underset{\uparrow }{b}}} \\\\ \cline{1-1} \end{array}`

so we're really looking for the equation of a line whose slope is -10/9 and it passes through (9 , -3) for line R

`(\stackrel{x_1}{9}~,~\stackrel{y_1}{-3})\hspace{10em} \stackrel{slope}{m} ~=~ - \cfrac{10}{9} \\\\\\ \begin{array}c \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}{(-3)}=\stackrel{m}{- \cfrac{10}{9}}(x-\stackrel{x_1}{9}) \implies y +3= -\cfrac{10}{9} (x -9) \\\\\\ y+3=-\cfrac{10}{9}x+10\implies {\Large \begin{array}{llll} y=-\cfrac{10}{9}x+7 \end{array}}`