Generally Speaking equation of a line is given by
Y = mx + b is a binomial ( contains 2 terms, one for X , and the other for constant)
m is the slope= difference in y coordinate of 2 points of the line/ difference in X coordinate of 2 points.
The distinct feature of a line is : that slope between every 2 points of a line is constant, and is that geometric property of line which leads to derive the equation as
Y = mx +b
Now another geometric property indicates that the relationship between slope of 2 perpendicular lines
(m1, m2 ) is such that:
m1 =  1/ m2
To put this into algebraic form
Consider 2 lines given:
L1 : m1 X + b1
L2 : m2 X + b2
L1 is perpendicular to L2
if and only if m1 =  1/m2
Here You have your L1 given as 4X 2y =10
Put it in the form of Y = m1x +b
and from there find out m2. By using the property explained in here.
3/8/2014

Parviz F.