Algebra
posted by Anonymous .
line l and and line k are perpendicular. line l has a slope of 3. line k contains the points (5,8) and (2, y). what is the value of y?

line l has slope 3, so line k haas slope 1/3
using the pointslope form of a line,
(y8) = 1/3 (x5)
3y24 = 5x
3y = 29x
so, if (2,y) is on the line,
3y = 292 = 27
y = 9
Or, without quite so much algebra, knowing that line k has slope 1/3, we know that y increases by 1 when x decreases by 3.
going from (5,8) to (2,y), x has decreased by 3, so y increases by 1, from 8 to 9.