Sign diagram

Below is the sign diagram for three linear expressions, denoted as , and (colour coded), where are constant whose value you can change by operating with your mouse on the sliders. Points , and indicate the points where each expression equals zero; continuous lines identify values of which render each expression positive, while the dashed lines refer to values of making an expression negative.]
Experiment with various values of and determine the sign of the expressions and algebraically with pen and paper. Then use the construction to check your results.