We have already seen how to solve a formula for a specific variable ‘in general’, so that we would do the algebraic steps only once, and then use the new formula to find the value of the specific variable. In this section we will derive and use a formula to find the solution of a quadratic equation. Mathematicians look for patterns when they do things over and over in order to make their work easier. By the end of the exercise set, you may have been wondering ‘isn’t there an easier way to do this?’ The answer is ‘yes’. When we solved quadratic equations in the last section by completing the square, we took the same steps every time. It may interest you to know that the completing the square process for solving quadratic equations was used on the equation ax 2 + bx + c = 0 to derive the quadratic formula.Solve Quadratic Equations Using the Quadratic Formula There is no solution in the real number system.
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Since the discriminant b 2 – 4 ac is negative, this equation has no solution in the real number system.īut if you were to express the solution using imaginary numbers, the solutions would be. The quadratic formula can also be used to solve quadratic equations whose roots are imaginary numbers, that is, they have no solution in the real number system.
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Since the discriminant b 2 – 4 ac is 0, the equation has one root.
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Then substitute 1, 2, and –2 for a, b, and c, respectively, in the quadratic formula and simplify. In Example, the quadratic formula is used to solve an equation whose roots are not rational. Then substitute 1 (which is understood to be in front of the x 2), –5, and 6 for a, b, and c, respectively, in the quadratic formula and simplify.īecause the discriminant b 2 – 4 ac is positive, you get two different real roots.Įxample produces rational roots. No real root if the discriminant b 2 – 4 ac is a negative number.One real root if the discriminant b 2 – 4 ac is equal to 0.Two different real roots if the discriminant b 2 – 4 ac is a positive number.A quadratic equation with real numbers as coefficients can have the following: The discriminant is the value under the radical sign, b 2 – 4 ac. These three possibilities are distinguished by a part of the formula called the discriminant. When using the quadratic formula, you should be aware of three possibilities. Where a is the numeral that goes in front of x 2, b is the numeral that goes in front of x, and c is the numeral with no variable next to it (a.k.a., “the constant”). A second method of solving quadratic equations involves the use of the following formula:Ī, b, and c are taken from the quadratic equation written in its general form of This is generally true when the roots, or answers, are not rational numbers. Many quadratic equations cannot be solved by factoring. To check, 2 x 2 + 2 x – 1 = x 2 + 6 x – 5 X 2 – 6 x = 16 becomes x 2 – 6 x – 16 = 0īoth values, 8 and –2, are solutions to the original equation.Ī quadratic with a term missing is called an incomplete quadratic (as long as the ax 2 term isn't missing).įirst, simplify by putting all terms on one side and combining like terms. Check by inserting your answer in the original equation.Put all terms on one side of the equal sign, leaving zero on the other side.To solve a quadratic equation by factoring, There are three basic methods for solving quadratic equations: factoring, using the quadratic formula, and completing the square. Quiz: Linear Inequalities and Half-PlanesĪ quadratic equation is an equation that could be written as.
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