TI-36X Pro—Replace the batteries or just get a new one?

[lrdheat]

Yet another plus concerning the TI-30X Pro MathPrint (and I'm guessing 36X Pro)...when looking for d/dx=0 for sqrt(abs(x^2 - 5)) in order to find a max or min, I had success with the 30X, but not with the CASIO 991EX which could only find an extremum at x=0, even if I chose an x very close to the -/+sqrt(5) value. I thought I would have better luck with the CASIO fx-CG50, but even with restricting the range to examine about sqrt(5), no success. The WP-34S was successful.