help please!!

The graph of which of the following will be perpendicular to the graph of y = 2x – 4?

A.
2x + y = 4
B.
4x – 2y = 4
C.
y = –2x + 8
D.
2x + 4y = 1

Question

help please!!

The graph of which of the following will be perpendicular to the graph of y = 2x – 4?

A.
2x + y = 4
B.
4x – 2y = 4
C.
y = –2x + 8
D.
2x + 4y = 1

anonymous · Answer

There are two things you should keep in mind.
1. Slope of line ax+by-c=0 is -a/b.
2. Two lines will be perpendicular if the product of their slopes is -1.
Here, Slope of given line y=2x-4 is 2. So, the line which is perpendicular to it should have a slope of -1/2. 
Now, Slope of line 2x+y=4 is -2.
Slope of line 4x-2y=4 is 2.
Slope of line y=-2x+8 is -2.
Slope of line 2x+4y=1 is -1/2.
So, Right ans. is D. 2x+4y=1.