Operations:   Finding coordinates of x-Intercepts


x-Intercepts are not just important "anchor" points on a graph.  They are the roots to a related equation. 

  1. Press Y= and enter the desired function.  For example:  y = x3 - 5x
  2. Press GRAPH:   wpe1.jpg (3768 bytes)wpe2.jpg (6580 bytes)
  3. To find an x-intercept , Press 2nd-TRACE (CALC)
  4. Press the "2" since zero is another name for x-intercept and root.
  5. Now the routine begins:  We will find the left-most zero
    wpe3.jpg (4568 bytes)

    The calculator needs an interval to "look" in. 
    So first, choose a spot along the graph that
    is to the LEFT of the intercept. 
    Do this by either entering a number,
    OR moving the arrow keys.
    Then hit ENTER

    bulletFollow the same procedure for the RIGHT bound. 
    The smaller the interval, the better.wpe7.jpg (4771 bytes)



    wpe9.jpg (4926 bytes)
    bullet"Guess" means, essentially, that the calculator wants a place in the interval to begin looking.   Either enter a number OR move the cursor as close to the intercept as possible, then press ENTER.

    wpeA.jpg (4354 bytes)
    The coordinates displayed at the bottom of the screen are those of the x-intercept.   Round as needed.






    Find any other x-Intercepts in the same way.

    HINT:  Sometimes, due to rounding errors, the Y value may not be exactly 0.  It may look like this:  1.03456787e-12

    Don't panic.  It's a number in scientific notation and is VERY small.   So small, it can be accepted as zero.