(first step:
you must remember the following theorem :
Two lines whose slopes are m1 and m2, are perpendicular if and only if m1m2 = -1
(second step
you have one slope given and it is -2 then you substitute in the previous equation
(third step
m1*-2=-1⇒m1=-1/-2⇒m1= 1/2
it means that new slope of the equation is 1/2
(for step
with a given point and a the slope you can build the equation that is perpendicular to a line with slope -2
the equation point- slope is
y-y1=m(x-x1)
with any given point as (2,-5) substitute it in the previous equation
[y-(-5)]= 1/2(x-2)⇒ (y+5) = 1/2x-1/4⇒y-1/2x+5+1/4⇒y-1/2x+21/4 =0
(five step
you must look for the value of x in the following equation
y-1/2x+21/4 =0
where, y = 1/2X-21/4 and this is the equation that represents a line that is perpendicular to a line with slope -2