Why is my TI84 Plus CE giving me incorrect answers when I take a derivative?

I recently purchased a TI84 Plus CE for my Calc II class. I tested it out, but the derivative function always reports answers which are incorrect. For

I recently purchased a TI84 Plus CE for my Calc II class. I tested it out, but the derivative function always reports answers which are incorrect. For example, when I do d/dx(1/x)|x=2, the answer should be -0.25 (since the derivative is -1/x^2). However, my calculator reports -0.2500000625. When I do d/dx(ln(x))|x=2, the answer should be 0.5 since the derivative is 1/x, however my calculator reports 0.5000000417. When I type in 1/2 or -1/(2^2) normally, it gives me a correct answer- it is only when I use the derivative function.

or:I recently purchased a TI84 Plus CE for my Calc II class. I tested it out, but the derivative function always reports answers which are incorrect. For example, when I do d/dx(1/x)|x=2, the answer should be -0.25 (since the derivative is -1/x^2). However, my calculator reports -0.2500000625. When I do d/dx(ln(x))|x=2, the answer should be 0.5 since the derivative is 1/x, however my calculator reports 0.5000000417. When I type in 1/2 or -1/(2^2) normally, it gives me a correct answer- it is only when I use the derivative function.

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