(10-31-2015 10:50 AM)Vtile Wrote: If the calculator is in exact mode set by user the CAS should behave according to that, while it is mathematically unorthodox solving answers like if user were using exact representation of given value instead of decimal value. In other words calculators CAS should expand (with silence or noting that "Unorthodox numerical format detected correcting user careless behaviour") the floating points to (36/10)²−4×(324/100) even if the user were typing the numbers in decimal format.

You misunderstand what the exact setting means. In CAS, you can perform exact *and* approx computations. If exact mode is set, the kind of computation is determined by the input (exact input, exact computation, approx input, approx computation). If approx mode is set, it means that all entries are considered as approx, even if they look like exact (in other words an evalf is done on the arguments).