What is the first step to show that two lines are perpendicular, by looking at the equations of the lines, if they are written in standard form?
a.
find the slope of each line.
b.
graph each equation.
c.
find the y-intercept of each line.
d.
re-write each equation in slope-intercept form.

Answer is D

First we need to Re-write them in slope-intercept form and than compare slopes of both lines.
You can tell that 2 lines are perpendicular if their slopes have relation:
k1 = -1/k2
where k1 is slope of first line and k2 is slope of second line.

Standard formula for line is:
ax + by = c

we transform that in this form:
y = kx + m where k is slope and m is intercept.

I'm not sure but i think it's 1670km/h