The original line . . . Y = -5x + 8
-- The slope of the line is -5 . It slopes down, 5 steps down for every step forward.
-- The y-intercept is 8 . The line crosses the y-axis at the point where y=8 .
= = = = =
The new line . . . Y = -125x + 8
-- The slope of the line is -125 . It slopes down, 125 steps down for every step forward. That's 25 times as steep as the original line.
-- The y-intercept is 8 . The line crosses the y-axis at the point where y=8 . That's the same as the original line.