find r so that the line through (2,6) and (-4,r) is perpendicular to x+2y=1

Question

find r so that the line through (2,6) and (-4,r)  is perpendicular to x+2y=1

tkhunny · Answer

x + 2y = 1 ==> Slope = -1/2  (Solve for y to find Slope-Intercept Form)

(r-6)/(-4-2) = 2 -- Where did the "2" come from?

anonymous · Answer

that's part of the equation how it was written in the book i am using

tkhunny · Answer

??  Did you solve it?

My question was the 2 that I wrote.  Where did I get get it.  It was not in your book.

anonymous · Answer

no, i don't

tkhunny · Answer

Except for horizontal (Slope is zero) and vertical (Slope doesn't exist) the slopes of perpendicular lines have this relationship...  $ Slope_{1}\cdot Slope_{2} = -1$

For you, the given line has slope -1/2.  Substitute that for $Slope_{1}$ and see where the algebra leads for $Slope_{2}$