Find the value of a if the line 2y – ax + 4 = 0 is perpendicular to the line y + (x/4) – 7 = 0
-
A.
-4 -
B.
4 -
C.
8 -
D.
-8
Correct Answer: Option C
Explanation
2y – ax + 4 = 0 (implies) 2y = ax – 4.
y + (x/4) – 7 = 0 (implies) y = -x/4 + 7
Slope of line 1 = a/2
Slope of line 2 = -1/4
-1/4 x a/2 = -1 (product of the slope of two perpendicular lines = -1)
a/8 = 1 (implies) a = 8.