A line on a coordinate grid passes through the points (-1, -3) and (4, 5). What is the slope of a line perpendicular to this line? Write the answer as a fraction in lowest terms.

Question

A line on a coordinate grid passes through the points (-1, -3) and (4, 5).  What is the slope of a line perpendicular to this line? Write the answer as a fraction in lowest terms.

danjs · Answer

can you find the slope of the line through those 2 points?

anonymous · Answer

how ?

danjs · Answer

recall:

slope = change in y value / change in x value = (y2-y1) / x2-x1)

danjs · Answer

Where a points given are (x1,y1) and (x2,y2)

danjs · Answer

$$slope = \frac{ 5 -(-3) }{ 4-(-1) } = ?$$

danjs · Answer

what is the slope of the given line with those 2 points?

anonymous · Answer

8/5 ?

danjs · Answer

ok correct, so we need a line that is perpendicular to that slope, to find the slope of that line,
flip the slope over and make it negative  (negative recipral)

What is the slope of the perpendicular line?

anonymous · Answer

-8/5?

danjs · Answer

close: you have to flip the fraction upside down, AND take the negative

danjs · Answer

THen, use that slope of the perpendicular line  m = (-5/8) and one of the points in the questin,(x1,y1), to form a equation of the perpendicular line,

y - y1 = m(x - x1)