Note in this example that the equation is already in standard form.Īgain, checking the solutions will assure you that you did not make an error in solving the equation. In this example 6 and -1 are called the elements of the set. The solutions can be indicated either by writing x = 6 and x = - 1 or by using set notation and writing, which we read 'the solution set for x is 6 and - 1.' In this text we will use set notation. If x = 6, then x 2 - 5x = 6 becomesĬhecking your solutions is a sure way to tell if you have solved the equation correctly. Step 4 Check the solution in the original equation.

This applies the above theorem, which says that at least one of the factors must have a value of zero. Since we have (x - 6)(x + 1) = 0, we know that x - 6 = 0 or x + 1 = 0, in which case x = 6 or x = - 1. Step 3 Set each factor equal to zero and solve for x. Solution Step 1 Put the equation in standard form. Of course, both of the numbers can be zero since (0)(0) = 0. We can never multiply two numbers and obtain an answer of zero unless at least one of the numbers is zero. We will not attempt to prove this theorem but note carefully what it states. In other words, if the product of two factors is zero, then at least one of the factors is zero. The method of solving by factoring is based on a simple theorem. This method cannot always be used, because not all polynomials are factorable, but it is used whenever factoring is possible. The simplest method of solving quadratics is by factoring. It is possible that the two solutions are equal.Ī quadratic equation will have two solutions because it is of degree two. This theorem is proved in most college algebra books.Īn important theorem, which cannot be proved at the level of this text, states 'Every polynomial equation of degree n has exactly n roots.' Using this fact tells us that quadratic equations will always have two solutions. The solution to an equation is sometimes referred to as the root of the equation. In other words, the standard form represents all quadratic equations. The standard form of a quadratic equation is ax 2 + bx + c = 0 when a ≠ 0 and a, b, and c are real numbers.Īll quadratic equations can be put in standard form, and any equation that can be put in standard form is a quadratic equation. Solve a quadratic equation by factoring.Ī quadratic equation is a polynomial equation that contains the second degree, but no higher degree, of the variable.

Place a quadratic equation in standard form.

Upon completing this section you should be able to: QUADRATICS SOLVED BY FACTORING OBJECTIVES You now have the necessary skills to solve equations of the second degree, which are known as quadratic equations. In previous chapters we have solved equations of the first degree. All skills learned lead eventually to the ability to solve equations and simplify the solutions. In these cases it is usually better to solve by completing the square or using the quadratic formula.Solving equations is the central theme of algebra. However, not all quadratic equations can be factored evenly. Step 4: Set each factor to zero and solve for x.Ģ.2: c = 15, a positive number, therefore both factors will be positive or both factors will be negative.Ģ.3: b = 8, a positive number, therefore the both factors will be positive.Ģ.2: c = -24, a negative number, therefore one factor is negative and the other is positive.Ģ.3: b = 10, a positive number, therefore the larger factor will be positive and the smaller factor negative.įactoring quadratics is generally the easier method for solving quadratic equations. Now that the equation has been factored, solve for x. If c is negative and b is positive, the larger factor will be positive and the smaller will be negative.Ģ.2: c = -14, a negative number, therefore one factor is negative and the other is positive.Ģ.3: b = 5, a positive number, therefore the larger factor will be positive and the smaller will be negative.Ĭreate two sets of parentheses each containing a x and one of the factors. If c is positive and b is negative, both factors will be negative. If both c and b are negative, the larger factor will be negative and the smaller will be positive. If both c and b are positive, both factors will be positive. Now create factor pairsĢ.3: Determine the factor pair that will add to give b. If c is negative then one factor will be positive and the other negative. If c is positive then both factors will be positive or both factors will be negative. Step 2: Determine the factor pair of c that will add to give b.įirst ask yourself what are the factors pairs of c, ignoring the negative sign for now. This equation is already in the proper form where a = 1, b = 5 and c = -14.

Factoring quadratic equation