Chapter 8: Problem 42
Solve each equation. Approximate the solutions to the nearest hundredth when appropriate. $$ x^{2}=-\frac{5}{4} x+\frac{3}{2} $$
Short Answer
Expert verified
The solutions to the equation are \( x = 0.75 \) and \( x = -2 \).
Step by step solution
01
Rearrange the Equation
First, let's rearrange the given equation into the standard form of a quadratic equation. The given equation is: \( x^2 = -\frac{5}{4}x + \frac{3}{2} \). To make it into standard form, move all terms to one side of the equation:\[ x^2 + \frac{5}{4}x - \frac{3}{2} = 0 \].This is now in the form \( ax^2 + bx + c = 0 \) with \( a = 1 \), \( b = \frac{5}{4} \), and \( c = -\frac{3}{2} \).
02
Identify a, b, and c
From the rearranged equation \( x^2 + \frac{5}{4}x - \frac{3}{2} = 0 \), we identify the coefficients as follows:\( a = 1 \), \( b = \frac{5}{4} \), \( c = -\frac{3}{2} \).
03
Apply the Quadratic Formula
The quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \) is used to find the roots of the quadratic equation. Substitute \( a = 1 \), \( b = \frac{5}{4} \), and \( c = -\frac{3}{2} \) into the formula:\[ x = \frac{-\frac{5}{4} \pm \sqrt{\left(\frac{5}{4}\right)^2 - 4 \cdot 1 \cdot \left(-\frac{3}{2}\right)}}{2 \cdot 1} \].
04
Calculate the Discriminant
Calculate the discriminant \( b^2 - 4ac \):\[ \left(\frac{5}{4}\right)^2 - 4 \times 1 \times \left(-\frac{3}{2}\right) = \frac{25}{16} + 6 = \frac{25}{16} + \frac{96}{16} = \frac{121}{16} \].
05
Compute the Square Root of the Discriminant
Take the square root of the discriminant:\[ \sqrt{\frac{121}{16}} = \frac{\sqrt{121}}{\sqrt{16}} = \frac{11}{4} \].
06
Solve for x using the Quadratic Formula
Substitute the square root of the discriminant back into the quadratic formula:\[ x = \frac{-\frac{5}{4} \pm \frac{11}{4}}{2} \].This gives us two possible solutions for \( x \):1. \( x = \frac{-\frac{5}{4} + \frac{11}{4}}{2} = \frac{6}{4} \div 2 = \frac{3}{4} \).2. \( x = \frac{-\frac{5}{4} - \frac{11}{4}}{2} = \frac{-16}{4} \div 2 = -2 \).
07
Approximate Solutions
Since we have found exact values that do not require approximations, our solutions are:\( x = \frac{3}{4} = 0.75 \) and \( x = -2 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Formula
In solving quadratic equations, the quadratic formula is a powerful tool that functions as a universal solver. With the formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \), you can find the solutions or roots of any quadratic equation in the form \( ax^2 + bx + c = 0 \), where \( a \), \( b \), and \( c \) are constants. From this formula, you can easily determine the values of \( x \) by using substitution for these constants.
Applying the formula breaks down into a straightforward process:
Applying the formula breaks down into a straightforward process:
- Substitute the values of \( a \), \( b \), and \( c \).
- Calculate the discriminant \( b^2 - 4ac \) to understand the nature of the roots.
- Solve for \( x \) by using both the plus and minus signs of the \( \pm \).
Discriminant Calculation
The discriminant is a key part of the quadratic formula, found under the square root: \( b^2 - 4ac \). Its value tells us important information about the roots:
- If the discriminant is positive, as in our solution with \( \frac{121}{16} \), there are two distinct real roots.
- If the discriminant is zero, there is exactly one real root or a repeated root.
- If the discriminant is negative, the equation has two complex roots.
Solving Quadratic Equations
Solving quadratic equations often means finding the solutions to equations of the form \( ax^2 + bx + c = 0 \). The solutions, or roots, are the values of \( x \) that satisfy the equation. Here's how you solve it step-by-step:
1. **Rearrange the equation** into the standard form so you can easily identify \( a \), \( b \), and \( c \).2. **Apply the quadratic formula** using the identified coefficients.
For instance, given \( a = 1 \), \( b = \frac{5}{4} \), and \( c = -\frac{3}{2} \), plug them into the formula.3. **Calculate the discriminant** to assess the nature of the roots and proceed to solve for \( x \) using both the plus and minus forms of the quadratic formula's square root component.
For the calculated discriminant of \( 121/16 \), solving leads to the solutions \( x = 0.75 \) and \( x = -2 \). By following these steps, you can confidently solve any quadratic equation and understand the behavior of its solutions.
1. **Rearrange the equation** into the standard form so you can easily identify \( a \), \( b \), and \( c \).2. **Apply the quadratic formula** using the identified coefficients.
For instance, given \( a = 1 \), \( b = \frac{5}{4} \), and \( c = -\frac{3}{2} \), plug them into the formula.3. **Calculate the discriminant** to assess the nature of the roots and proceed to solve for \( x \) using both the plus and minus forms of the quadratic formula's square root component.
For the calculated discriminant of \( 121/16 \), solving leads to the solutions \( x = 0.75 \) and \( x = -2 \). By following these steps, you can confidently solve any quadratic equation and understand the behavior of its solutions.