√-47 is usually written as i √47 indicating it’s an imaginary number. Problem: Find the nature of roots for the equation x 2+x+12 = 0.ī 2-4ac = -47 for this equation. If b 2-4ac < 0, the roots are not real (they are complex). If b 2-4ac = 0, the roots are real and equal. If b 2-4ac > 0, the roots are real and distinct. But let’s solve it using the new method, applying the quadratic formula.įor an equation ax 2+bx+c = 0, b 2-4ac is called the discriminant and helps in determining the nature of the roots of a quadratic equation. So this can be solved by the factoring method. What are the two numbers which when added give +10 and when multiplied give -24? 12 and -2. Rewriting the equation into the standard quadratic form, Hence, √7-1 and -√7-1 are the roots of this equation. Here 28 can be expressed as a product of 4 and 7. When we get a non-perfect square in a square root, we usually try to express it as a product of two numbers in which one is a perfect square. Substituting these values in the formula, Now, let us find the roots of the equation above.
Hence this quadratic equation cannot be factored.įor this kind of equations, we apply the quadratic formula to find the roots. If we take +3 and -2, multiplying them gives -6 but adding them doesn’t give +2. But this method can be applied only to equations that can be factored.įor example, consider the equation x 2+2x-6=0. The factoring method is an easy way of finding the roots. This can be done by expressing 18x as the sum of 11x and 7x. In this case, the sum of the numbers we choose should equal to 18 and the product of the numbers should equal 11*7 = 77. Therefore, the product of the numbers we choose should be equal to -3 (-1*3). In these cases, we multiply the constant c with the coefficient of x 2. Rewriting our equation, we get 3x 2+2x-1= 0 Let us see how to solve the equations where the coefficient of x 2 is greater than 1. The numbers which add up to -18 and give +45 when multiplied are -15 and -3. Let us express -3x as a sum of -5x and +2x. Let us solve some more examples using this method. The roots of this equation -2 and -3 when added give -5 and when multiplied give 6. Sum of the roots for the equation x 2+5x+6 = 0 is -5 and the product of the roots is 6. We saw earlier that the sum of the roots is –b/a and the product of the roots is c/a. Let us express the middle term as an addition of 2x and 3x.
We have to take two numbers adding which we get 5 and multiplying which we get 6. Now, let’s calculate the roots of an equation x 2+5x+6 = 0.
Here, a and b are called the roots of the given quadratic equation. The sum of its roots = –b/a and the product of its roots = c/a.Ī quadratic equation may be expressed as a product of two binomials.įor example, consider the following equation These are called the roots of the quadratic equation. The following are examples of some quadratic equations:įor every quadratic equation, there can be one or more than one solution. In this article we cover quadratic equations – definitions, formats, solved problems and sample questions for practice.Ī quadratic equation is a polynomial whose highest power is the square of a variable (x 2, y 2 etc.) DefinitionsĪ monomial is an algebraic expression with only one term in it.Ī polynomial is an algebraic expression with more than one term in it.Ī polynomial is formed by adding/subtracting multiple monomials.Įxample: x 3+2y 2+6x+10, 3x 2+2x-1, 7y-2 etc.Ī polynomial that contains two terms is called a binomial expression.Ī polynomial that contains three terms is called a trinomial expression.Ī standard quadratic equation looks like this:Ī, b are called the coefficients of x 2 and x respectively and c is called the constant.