Did you sketch the graphs?
Determine the number of solutions of the following system, depending on the value of .
The graph of  looks like this:Code:| 1* * | * * | * * | * - - * - - - + - - - * - - -1 * | * 1 * | * * | * -1* |
The graph of  looks like this:Code:| * | * * | * * | * * | * a* | - - - - - - + - - - - - - |
Superimpose the two graphs and "slide" up and down the y-axis
. . and you will observe the following . . .