Sequence returning elements with "?"'s -- yet commands typed correctly
In attached applet, my immediate goal is to plot any holes the graph of a rational function may have. My means of doing so are as follows:
rootsd = roots of denominator
rootsn = roots of numerator
commonroots = roots of BOTH numerator & denominator (for which graph of rational function will have a hole at these x-value(s))
I created a sequence called lines that has x = any number value from commonroots.
Then, when I created the holes list, I got points back with (?, ?) for coordinates.
In the example shown in attached file, the rational function has 2 holes (one at (-1, r(-1)) and (0, r(0)). Yet WHY am I getting this? I believe I typed in commands correctly.
Thank you in advance for any help you can provide.