Students represent nonvertical linear relationships in equations, tables, graphs, and verbal descriptions, identifying slope as the constant rate of change and the y-intercept as the initial value. They determine slope from graphs, tables, or two points, interpret its sign, magnitude, and units, and write or graph equations in the form $y=mx+b$. They compare linear functions across representations by analyzing rates of change, initial values, outputs at given inputs, and intersections, recognizing that lines may change which function is greater after crossing.