With yx = zx, then by the Multiplicative Property of Equality, y = z. Since z is a negative integer, then y is also a negative integer. Since yx is positive, with y equal to a negative integer, then x is negative.
These two slope values are positive. Positive slopes correspond to lines that move uphill as you move from left to right.
A negative slope moves in the opposite direction. A slope of zero refers to a flat horizontal line. A slope of undefined means we have a vertical line.
