Answer
The slope of a line perpendicular to the given line $-1$.
Work Step by Step
RECALL:
$\\\\$(i) In the function f(x)=mx+b, m=slope and b=y-intercept.
$\\\\$(ii) Perpendicular lines have the slopes that are negative reciprocals of each other (a product of -1).
$\\\\$The given function has a slope of $1$.
$\\\\$Perpendicular lines have the slopes whose product is -1 (negative reciprocals of each other) therefore the slope of a line perpendicular to the given line $-1$.
