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I am currently completing a water engineering subject at university as part of my civil engineering studies. For this subject (and probably others in future), I occasionally need to solve for an unknown value in a quadratic or cubic function, where there are three possible solutions and I need to know all three (to do with depths in open channel flows, one is negative so we discard it, one is for subcritical flow, and the other is for supercritical flow).

I own three HP calculators, the 42S, the 11C and the 48G (having heard only good things about them), and only the 48G has an algrebraic equation solver which would be useful in such a scenario. I thought the 48G would be able to solve these problems in an instant, but instead I find when using the equation solver that it never gives me more than one answer, even for a quadratic (no matter how many times I press 'solve'). I tried looking in the user guide but couldn't see anything that offered any clues.

Am I simply doing something wrong, or does the equation solver on this machine only give one answer? I can't believe it couldn't handle something so basic.

If it's a calculator and not an operator problem, could someone please recommend me a calculator that can handle these sorts of problems quickly, for use in my final exam in June. We are allowed to use graphics calculators in our exams, even programmable ones, but programming isn't necessary for me. It wouldn't have to be HP (or RPN, but I do prefer that), a Ti would be fine, just anything quick and efficient that works.

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# HP 48G equation solver and multiple solutions

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