Completing the Squares

Completing the Squares

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Mastering Completing the Square for Solving Quadratic Equations

In the world of algebra, simplifying expressions is key to identifying patterns and solving equations. For quadratic equations, we often use methods like factoring or identifying the greatest common factor. However, there is another powerful technique called completing the square that we'll explore in this article. Not only does it simplify quadratic equations, but it also helps us find their maximum or minimum values and aids in graphing.

The Concept of Completing the Square

An expression in the form of (x+a)2 or (x-a)2 is known as a complete square. By expanding these expressions, we obtain (x+a)(x+a) = x2+2ax+a2 and (x-a)(x-a) = x2-2ax+a2, respectively. Completing the square is a method used to convert a quadratic equation into a simpler algebraic expression that can be easily solved. This also allows us to represent the equation in the vertex form, which is useful in graphing and determining extrema points.

The Formula for Completing the Square

To complete the square of a quadratic equation, we need to convert it into the form (x-h)2 + k = 0, where h = b2a and k = c-b24a. This formula is known as the vertex form of a quadratic equation.

A Geometrical Perspective

To better understand completing the square, let's take a look at the diagram below. We have a red square and a green rectangle, which, when combined, represent the expression x2+bx. To simplify it, we halve the width of the green rectangle to obtain b22. Rearranging the two smaller green rectangles, we have the second image. However, to complete the square, we need to add the area of the blue square, b22. This results in the third image, which can be represented algebraically as x2+bx+b22=x+b22, where the term b22 completes the square.


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