coordinate geometry

Question

Find the value of a if the lines 2y-ax+4=0 is perpendicular to the line y+1/4x-7=0

Answer 1

y + (1/4)x - 7 = 0     Solve for y

y = -(1/4)x + 7         The slope of this line is -1/4. Perpendicular lines have slopes that are negative reciprocals of each.

2y - ax + 4 = 0          Solve for y

2y = ax - 4

y = (a/2)x - 2 

 

a/2 = 4

a = 8