Answer:
-1/3
Explanation:
Write the equation in a slope intercept form,
y= mx +b , where m = slope, b = y-intercept.
3x - y = 4, subtract 3x from both sides
-y = -3x +4 , multiply both sides by -1
y = 3x - 4, here slope = 3 and y-intercept = -4
Perpendicular lines have their slopes negative reciprocal so the slope of a line perpendicular to 3x - y = 4 also written as y = 3x -4 is m= -1/3