Line ef has an equation of a line y = −2x + 7. which of the following could be an equation for a line that is perpendicular to line ef?

y = 2x − 3
y = 1 over 2x − 3
y = −2x − 3
y = −1 over 2x − 3

1.

When a line is given in the form y=mx+n, 

m is the slope of this line.

For example, the slope of the line y=-2x+7 is -2.

2. 

If lines y=mx+n and y=kx+t are perpendicular, then the multiplication of their slopes is -1, that is

m*k = -1, so k=-1/m

3.

any line perpendicular to y=-2x+7 has slope = -1/(-2)=1/2

4.

Among the choices, y=(1/2)x-3 is a line perpendicular to the given line.

 

b. y=(1/2)x-3