Question

Which graph represents a proportional relationship?
On a coordinate plane, a straight line with negative slope goes through points (2, 6), (4, 5).
On a coordinate plane, a curve opens down.
On a coordinate plane, a straight line with positive slope goes through points (5, 2) and (6, 3).
On a coordinate plane, a straight line with positive slope goes through points (3, 3) and (4, 4).

Answer 1

A proportional relationship is a line through the origin (y = kx). The line through (3,3) and (4,4) has slope 1 and equation y = x, which goes through (0,0). So the fourth graph represents a proportional relationship (with k = 1).