Are the lines y = –x – 4 and 5x -5y = 20 perpendicular? Explain.

yes

Step-by-step explanation:

If 2 lines are perpendicular then the product of their slopes = - 1

The equation of a line in slope- intercept form is

y = mx + c ( m is the slope and c the y- intercept )

y = - x - 4 ← is in slope- intercept form

with slope m = - 1

5x - 5y = 20 ( subtract 5x from both sides )

- 5y = - 5x + 20 ( divide all terms by - 5 )

y = x - 4 ← in slope- intercept form

with slope m = 1

Thus product of their slopes is - 1 × 1 = - 1

Therefore the lines are perpendicular

irrational, cannot