Final answer:
A diagonal line sloping upward on a graph indicates a positive slope, which means the y-value increases as x increases. The steepness of the slope is determined by the value of the slope; a steeper line has a higher positive or more negative value. A slope of zero represents a horizontal line with no vertical movement.
Step-by-step explanation:
The slope of a line on a graph tells you the direction and steepness of the line as it travels across the coordinate system. If a line is sloping diagonally toward the upper portion of the graph, this indicates a positive slope. A positive slope means that the line moves up the y-axis as the x-value increases. Conversely, a negative slope means that the line moves down the y-axis. The steepness is determined by the magnitude of the slope value: the greater the value, positive or negative, the steeper the line.
Graphically speaking, if the slope of a line increases, the line becomes steeper. If the slope decreases, the line becomes flatter. A slope of zero corresponds to a horizontal line, which represents no motion in horizontal and vertical motion contexts, like in physics. If the context of the graph changes, such as in economics, a horizontal line could represent a constant function.