A line is perpendicular to
y = -3x – 9
What is the slope of this
perpendicular line?

Answer:
a. 1/3
In the picture- D. 4
Explanation:
The product of the gradients of perpendicular lines =-1
m1m2=-1
Given an equation of a line in the form y=mx+c, m is the gradient of the line.
For y= -3x-9, m=-3
m1m2=-1
-3×m2=-1
m2=1/3
The gradient of the perpendicular line is 1/3
For the question in the picture, y=-1/4x-9, m=-1/4
m1×m2=-1
-1/4m2=-1
m2=4
The slope of the line perpendicular to y=-1/4x-9 is 4
Answer:
The correct answer option is D. 4.
Explanation:
We are given that a line is perpendicular to another line with the equation [tex]y=-\frac{1}{4} x-9[/tex]. We are to find the slope of this perpendicular line.
We know that the in the standard equation of a line, [tex]y=mx+c[/tex], m is the slope of the line.
Also, the slope of a line perpendicular to another is the negative reciprocal of that line.
Therefore, the slope of this perpendicular line is 4.