Downhill Lines

A line with a negative slope goes down as you move right. Each step to the right takes you down instead of up. The line $y = -2x+4$ has slope $-2$, so it goes down 2 for every step right. The minus sign tells you the line falls.

Slope -2 falls as fast as slope 2 climbs

The slope tells you two separate things. The size of the slope tells you how steep the line is. The sign tells you the direction. In the figure, the slopes 2 and $-2$ are equally steep, but one line goes up and the other goes down. A slope close to 0, like $\frac{1}{10}$ or $\frac{-1}{10}$, gives a line that is nearly flat.