The Point-Slope Form of a Linear Equation
The point-slope form of a linear equation is .
Move slider . The slope is . See the steepness of the line change. 
When  is negative, the direction of the line changes. 
When , the line is flat.
Move slider  and . These make the point . 
When there is only one point, the slope and the point can be used to find the equation of a line.