We know that :
Ф Product of the slopes of two lines perpendicular to each other should be equal to -1
Let the slope of the line perpendicular to given line be : M
Given equation of the line : y = -1/2x + 4
This line is in the form : y = mx + c, where m is the slope and c is the y intercept
Comparing with y = mx + c :
we can notice that slope of the given line is -1/2
⇒ M × -1/2 = -1
⇒ M × 1/2 = 1
⇒ M = 2
Answer : Slope of the line perpendicular to given line is 2