Poly-Q1.md

Solve for $x$: $(x -1)(x +2)(x-3)(x+4) >0$

Form a sign table

A good example is https://www.youtube.com/watch?v=idBbsanc8BQ by MySecretMathTutor

x	(- $\infty$ ,-4)	-4	(-4,-2)	-2	(-2,1)	1	(1,3)	3	(3, $\infty$)
x-1	-	-	-	-	-	0	+	+	+
x+2	-	-	-	0	+	+	+	+	+
x-3	-	-	-	-	-	-	-	0	+
x+4	-	0	+	+	+	+	+	+	+
f(x)	+	0	-	0	+	0	-	0	+

So the solution set for the inequality is

$x \in (- \infty ,-4) \cup (-2,1) \cup (3, \infty)$