Question

determine the slope of the line.

(1, 2) and (2, 1)

Answer 1

the slope of a line can also be calculated as y2-y1/x2-x1

so assign y1 and y2 (1 and 2 respectively)
and assign x1 and x2 (2 and 1 respectively)

y2-y1/x2-x1
1-2/2-1
-1/1

=-1 slope