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Quadratic equation

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A math diagram showing how changing numbers in a quadratic equation changes the shape of its graph.

What is a Quadratic Equation?

A quadratic equation is a fun math puzzle that helps us find missing numbers. It looks like this: a × x² + b × x + c = 0. Here, x is the number we need to find, and a, b, and c are numbers we already know. The letter a must not be zero, or it would not be a quadratic equation.

Quadratic equations are special because they can have up to two answers. These answers are called solutions or roots. Sometimes, both answers are the same, and this is called a double root.

Solving Quadratic Equations

There are many ways to solve quadratic equations. One easy way is to use the quadratic formula: x = (−b ± √(b² − 4a**c)) / (2a). This formula gives us the answers directly. People have been solving problems that lead to quadratic equations for thousands of years, as early as 2000 BC.

Quadratic equations can have zero, one, or two solutions. When there is only one answer, it is called a double root. When there are no real answers, the equation still has two special answers called complex numbers.

Why Quadratic Equations are Important

Quadratic equations are used in many places. They help us understand shapes like circles, ellipses, parabolas, and hyperbolas. In physics, quadratic equations help predict how things move when they speed up the same way all the time. They are also important in chemistry for finding out how sour or basic some liquids are.

People from many countries, like Babylon, Egypt, Greece, China, and India, used quadratic equations long ago. An Indian mathematician named Brahmagupta found one of the first formulas to solve these equations. Later, a smart person named Muhammad ibn Musa al-Khwarizmi made new ways to solve them. Today, we use the quadratic formula just like they did, but in a form we use now.

Images

A diagram showing how to find the roots of a quadratic equation using mathematical methods.

This article is a child-friendly adaptation of the Wikipedia article on Quadratic equation, available under CC BY-SA 4.0.

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