Posted by vmu on .
The perpendicular bisector of the line joining the points D(1,2) and E(5,4) meets the yaxis at the point (0,k).calculate k

maths 
Steve,
First, find the midpoint of DE: ((1+5)/2,(2+4)/2) = (3,3)
Now, find the slope of the line DE: (42)/(51) = 2/4 = 1/2
You want a perpendicular line, so its slope will be 2
The equation of the desired line, using pointslope form:
(y3)/(x3) = 2
y3 = 2x + 6
y = 2x + 9
The yintercept is (0,9) so k=9