How do you solve #-9 <= -3x+15 <= 12#?
Let us start with a graph of the inequality:
If we define
Reading directly on the graph, we see that
Mathematically we would solve it by treating the two inequalities separately:
Add 3x-12 on both sides to move 3x to one side and the constants to the other:
The values for x fulfilling the inequality is, therefore
Which is what we could read directly from the graph.