Yes, you can solve a limit at infinity using a calculator, but all things being equal, it’s better to solve the problem algebraically, because then you have a mathematically airtight answer. For example, with the problem,


the calculator answer of 0.5 is very convincing, but it’s not mathematically rigorous, so if you stop there, the math police may get you.

  1. Try substitution — always a good idea.

    No good. You get ∞ – ∞, which tells you nothing. On to plan B.

  2. Multiply the numerator and denominator by the conjugate of


    and simplify.

  3. Now substitution does work.