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Videos to explain Standard Deviation Formula, Fibonacci Formula, Completing the square and Quadratic Formula.

Standard Deviation Formula Explained

The formula for standard deviation looks scary and feels scary. Why on earth would anyone want to measure a sense of "spread" of data values with a formula like that??!!!? Well, let me tell you the very natural and very human story that explains why.

The Fibonacci numbers begin 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, .... What's the 100th number in this list? The 587th number? In this video we derive a general formula the N-th Fibonacci number.

(WARNING: This video assumes complete familiarity with solving a quadratic equation, basic properties of exponents, and solving a tiny system of equations.)

Here's the simple way to solve quadratic equations by completing the square.

Here's the second section of video on how to solve quadratics with ease.

Deriving the Quadratic Formula

After learning how to complete the square, see how quickly and magically the famous quadratic formula pops out at you!

Rotate to landscape screen format on a mobile phone or small tablet to use the **Mathway** widget, a free math problem solver that **answers your questions with step-by-step explanations**.

You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.