Linear Algebra For Dummies
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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,

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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.

    image1.png
  2. Multiply the numerator and denominator by the conjugate of

    image2.png

    and simplify.

    image3.png
  3. Now substitution does work.

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Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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