Browse the Gizmo Collection. Explore the properties of a straight line graph. Move the m and b slider bars to explore the properties of a straight line graph. Look at The effect of changes in m The effect of changes in b The effect of a negative value of m The effect of a negative value of b How to create a horizontal line Read more about the Equation of a Straight Line Now see how two points can change the line equation. Y = 2x + 1 y = -2x -1 y = x y = 1 x = 1. Number Cruncher. Linear Function Machine. Equation Grapher 2.02.