Chapter 1: Problem 15
Solve the equation by using the quadratic formula. $$ 2 x^{2}-3 x-4=0 $$
Short Answer
Expert verified
The solutions are \(x = \frac{{3 + \sqrt{41}}}{4}\) and \(x = \frac{{3 - \sqrt{41}}}{4}\).
Step by step solution
01
Identify Components of the Quadratic Equation
First, identify the coefficients \(a\), \(b\), and \(c\) from the quadratic equation \(2x^2 - 3x - 4 = 0\). In this equation, \(a = 2\), \(b = -3\), and \(c = -4\).
02
Write Down the Quadratic Formula
The quadratic formula is given by \(x = \frac{{-b \pm \sqrt{{b^2 - 4ac}}}}{2a}\). We'll use this formula to find the roots of the equation.
03
Calculate the Discriminant
Compute the discriminant, \(b^2 - 4ac\). Substituting the values of \(b\), \(a\), and \(c\), we get \((-3)^2 - 4(2)(-4) = 9 + 32 = 41\). The discriminant is 41.
04
Substitute into the Quadratic Formula
Substitute \(a\), \(b\), \(c\), and the discriminant into the quadratic formula: x = \frac{{-(-3) \pm \sqrt{41}}}{2(2)} = \frac{{3 \pm \sqrt{41}}}{4}.
05
Simplify the Expression
Now, simplify the quadratic formula to find the two possible values of \(x\):\(x_1 = \frac{{3 + \sqrt{41}}}{4}\) and \(x_2 = \frac{{3 - \sqrt{41}}}{4}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equation
A quadratic equation is a type of polynomial equation of the second degree, which means the highest exponent of the variable is 2. The standard form of a quadratic equation is given as \( ax^2 + bx + c = 0 \), where \( a \), \( b \), and \( c \) are constants and \( a \) cannot be zero. Quadratic equations are fundamental in algebra and appear in various mathematical contexts and real-world applications.
When graphed on a coordinate plane, a quadratic equation forms a parabola, which can open upwards or downwards depending on the sign of \( a \). Solving a quadratic equation can be done through various methods such as factoring, completing the square, or using the quadratic formula.
When graphed on a coordinate plane, a quadratic equation forms a parabola, which can open upwards or downwards depending on the sign of \( a \). Solving a quadratic equation can be done through various methods such as factoring, completing the square, or using the quadratic formula.
Discriminant
The discriminant is a crucial component in the analysis of quadratic equations. It is denoted by \( b^2 - 4ac \) and comes from the quadratic formula. The discriminant determines the nature of the roots of the quadratic equation:
For the given equation \( 2x^2 - 3x - 4 = 0 \), we calculated the discriminant as 41, which is positive. Therefore, we expect two distinct real roots for this equation.
- If the discriminant is positive, there are two distinct real roots.
- If it is zero, there is exactly one real root, also known as a repeated or double root.
- If the discriminant is negative, the equation has two complex roots, which are conjugates of each other.
For the given equation \( 2x^2 - 3x - 4 = 0 \), we calculated the discriminant as 41, which is positive. Therefore, we expect two distinct real roots for this equation.
Roots
The roots, or solutions, of a quadratic equation are the values of \( x \) that satisfy the equation. These roots can be found using the quadratic formula: \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \).
In the case of the equation \( 2x^2 - 3x - 4 = 0 \), with a positive discriminant of 41, the roots are calculated as follows:
In the case of the equation \( 2x^2 - 3x - 4 = 0 \), with a positive discriminant of 41, the roots are calculated as follows:
- Root 1: \( x_1 = \frac{3 + \sqrt{41}}{4} \)
- Root 2: \( x_2 = \frac{3 - \sqrt{41}}{4} \)
Coefficients
Coefficients in a quadratic equation are the constants \( a \), \( b \), and \( c \). They define the characteristics of the quadratic equation:
For the equation \( 2x^2 - 3x - 4 = 0 \), we have the coefficients \( a = 2 \), \( b = -3 \), and \( c = -4 \). Understanding these helps in predicting and graphing the behavior of the quadratic equation.
- \( a \) is the leading coefficient and affects the direction and width of the parabola.
- \( b \) influences the position of the vertex of the parabola along the x-axis.
- \( c \) is the constant term and determines the y-intercept of the parabola on the graph.
For the equation \( 2x^2 - 3x - 4 = 0 \), we have the coefficients \( a = 2 \), \( b = -3 \), and \( c = -4 \). Understanding these helps in predicting and graphing the behavior of the quadratic equation.