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Mathematics LibreTexts

6.1: Why It Matters- Factoring

  • Page ID
    51468
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    Why learn how to factor?

    Car with boxes strapped to the top in a way that looks like they will fall off.
    Moving Madness

    The way you organize your belongings when you move can have a huge impact on the success of your move. For example, you wouldn’t want to try and move all your things using only shoeboxes. Not only would it take forever, you probably own things that are larger than a shoebox. Storing and sorting the nuts and bolts in your toolshed is very different from storing and sorting all of your possessions when you move.

    In this module, we will present some factoring techniques for polynomials that will help you solve polynomial equations. Factoring is a complementary operation to the distributive property, it is a way to “unpack” the multiplication done by applying the distributive property. Reorganizing polynomials by factoring allows us to find solutions for certain types of polynomials.

    You may be thinking, we already know how to solve linear equations, why don’t we just use the same techniques for solving polynomial equations? Let’s investigate the example below to see why we need different techniques for solving polynomial equations than for solving linear equations with an example.

    Solve the following second degree polynomial equation: \(x^2+6x-7=2x-4\)

    We use complementary operations to isolate the variable when we solve linear equations, so we will try to do the same with this polynomial equation.

    \(\begin{array}{l}x^2+6x-7=2x-4\\\,\,\,\,\,\,\,\,\underline{-2x}\,\,\,\,\,\,\,\,\,\,\,\,\,\underline{-2x}\,\,\,\,\,\,\\x^2+4x-7=-4\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\underline{+7}\,\,\,\,\,\,\,\,\,\underline{+7}\\x^2+4x=3\end{array}\)

    Ok, now what? We could try dividing all the terms by 4 to isolate x, but we would still have \(x^2\). We will need different techniques than we use for solving linear equations to solve this equation. There are many methods for solving different kinds of polynomials using algebraic principles, but the truth is that most polynomials cannot be solved with the algebra we have used here.

    At the end of this module, we will share some of the practical uses for solving polynomials that occur in our everyday lives. Polynomials are everywhere! They appear in electrical circuitry, mechanical systems, population ecology, roller coaster design, classrooms around the US, and even in the way Google’s search engine ranks pages.

    Learning Outcomes

    • Simple Polynomial Equations
      • Use the zero product principle
      • Identify the greatest common factor of a polynomial
      • Solve simple polynomial equations
    • Factoring Methods
      • Factor by grouping
      • Factor trinomials
    • Applications of Trinomials
      • Solve quadratic equations
      • Solve quadratic equations involving projectile motion
      • Use the pythagorean theorem