Explore Roots and Sign
Define:
f(x) := (x + 3)(x - 1)^2(x - 4)
Solve:
Solve[$1 < 0, x]
Where does the function graph cross the x-axis vs. touch it? Why is the solution open at x = 1?
Check the Signs near interesting values
Substitute[f(x), x = -4]
Substitute[f(x), x = 0]
Substitute[f(x), x = 1]
Substitute[f(x), x = 5]