Slope+discussion

Positive slope • Lines that have positive slope, slant "up hill“ (as viewed from left to right).

Zero slope • Lines that are horizontal have zero slope i.e. energy level is zero.

Negative slope • Lines that have negative slope, slant "down hill“ (as viewed from left to right).

Undefined/No slope • Vertical lines have no slope, or undefined slope.

http://regentsprep.org/Regents/math/glines/Llines.htm

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