Note that you must specifiy both an X range and Y range when using this command. Graph the following lines using the implicitplot command as shown above. Its interesting to see at a glance how changing a function, changes its graph. The blue curves indicate what happens when k is positive, and the red ones indicate what happens when k is negative. You can see that when k is added, the blue graphs result, and when k is subtracted the red curves result.
Every parabola has a vertex and axis of symmetry.
With these commands you will see these features on the graph with the parabola. The axis of symmetry is the dark blue vertical line. The vertex of the parabola is identified by a small red diamond where the horizontal and vertical lines cross. Copy and paste the block of commands above. Change the values of a and b and execute the block.