Differential Equations For Dummies
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You can solve quadratic equations by completing the square. Completing the square involves creating a perfect square trinomial from the quadratic equation, and then solving that trinomial by taking its square root.

  1. Put the x-squared and the x terms on one side and the constant on the other side.

  2. Divide both sides by the coefficient of x-squared (unless, of course, it’s 1).

  3. Take half of the coefficient of x, square it, then add that to both sides.

  4. Factor the left side.

    Notice that the factor always contains the same number you found in Step 3 (–4 in this example).

  5. Take the square root of both sides.

  6. Solve.


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Steven Holzner was an award-winning author of more than 130 books, of which more than 2 million copies have been sold. His books have been translated into 23 languages. He served on the Physics faculty at Cornell University for more than a decade, teaching both Physics 101 and Physics 102. Holzner received his doctorate in physics from Cornell and performed his undergraduate work at Massachusetts Institute of Technology, where he also served as a faculty member.

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