As you drag the slider above, watch how the sign of each of the factors of [math]f\left(x\right)[/math] changes. Each factor changes signs exactly once, as you pass its critical value. This is why the roots are called critical values, because they are the [math]x[/math]-values at which the sign of the corresponding factors changes.[br][br]If you want to see what the numerical value of each factor is, then check the "Numbers" box.