Answer:
perpendicular slope = 1
Explanation:
the equation of a line in slope- intercept form is
y = mx + c ( m is the slope and c the y- intercept )
given
x + y = 9 ( subtract x from both sides )
y = - x + 9 ← in slope- intercept form
with slope m = - 1
given a line with slope m then the slope of a line perpendicular to it is
= -
= -
= 1