Chapter 7: Problem 21
Solve the given quadratic equations by completing the square. $$2 s^{2}+5 s=3$$
Short Answer
Expert verified
The solutions are \( s = \frac{1}{2} \) and \( s = -3 \).
Step by step solution
01
Rearrange the Equation
First, move the constant term to the right side of the equation. Given is \( 2s^2 + 5s = 3 \). Subtract 3 from both sides to get \( 2s^2 + 5s - 3 = 0 \). Divide the entire equation by 2 to prepare for completing the square, resulting in \( s^2 + \frac{5}{2}s = \frac{3}{2} \).
02
Prepare for Completing the Square
Identify the coefficient of \( s \) (which is \( \frac{5}{2} \)) and take half of it, resulting in \( \frac{5}{4} \). Then, square it to get \( \left(\frac{5}{4}\right)^2 = \frac{25}{16} \). Add and subtract this square inside the equation.
03
Complete the Square
Add and subtract \( \frac{25}{16} \) inside the left side of the equation: \( s^2 + \frac{5}{2}s + \frac{25}{16} - \frac{25}{16} = \frac{3}{2} \). The expression with the added square becomes \( (s + \frac{5}{4})^2 \). Thus, the equation changes to \( (s + \frac{5}{4})^2 - \frac{25}{16} = \frac{24}{16} \) upon converting \( \frac{3}{2} \) to \( \frac{24}{16} \).
04
Isolate the Square
Add \( \frac{25}{16} \) to both sides to isolate the complete square: \( (s + \frac{5}{4})^2 = \frac{49}{16} \).
05
Solve for \( s \)
Take the square root of both sides: \( s + \frac{5}{4} = \pm \frac{7}{4} \). Solve for \( s \) by subtracting \( \frac{5}{4} \) from both possible solutions, yielding \( s = \frac{7}{4} - \frac{5}{4} = \frac{1}{2} \) and \( s = -\frac{7}{4} - \frac{5}{4} = -3 \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equations
Quadratic equations play a crucial role in algebra and appear in various mathematical contexts. These equations are of the form \( ax^2 + bx + c = 0 \), where \( a \), \( b \), and \( c \) are constants, and \( a eq 0 \). The highest degree of the variable \( x \) is 2, hence the name "quadratic." Understanding how to solve them is essential for progression in mathematics.
Quadratic equations can represent various real-world scenarios such as projectile motion or area problems. Solving these equations requires fundamental algebraic strategies, including:
Quadratic equations can represent various real-world scenarios such as projectile motion or area problems. Solving these equations requires fundamental algebraic strategies, including:
- Factoring
- Using the quadratic formula
- Completing the square
Step by Step Solution
Following a clear step-by-step approach is indispensable when solving quadratic equations by completing the square. It’s like unraveling a mystery, one piece at a time. Let’s break it down further to understand what it entails.
**Step 1: Preparation and Rearrangement**
Initially, the equation should be rearranged by moving terms around so that it's set to zero. For the equation \( 2s^2 + 5s = 3 \), rearranging it leads to \( 2s^2 + 5s - 3 = 0 \), then dividing by 2 prepares it for completing the square.
**Step 2: Completing the Square**
Half of the coefficient of \( s \) is determined and squared. This square, when added and subtracted ingeniously, enables the left side of the equation to factor into a perfect square trinomial, expressed as \( (s + \frac{5}{4})^2 \), streamlining the path towards the solution.
**Step 3: Isolating and Solving**
Finally, isolate the square on one side and solve by taking the square root. This provides potential solutions for \( s \) through simple arithmetic, leading to both possible solutions for the variable.
This method is detailed and logical, offering a robust toolset to tackle quadratic equations.
**Step 1: Preparation and Rearrangement**
Initially, the equation should be rearranged by moving terms around so that it's set to zero. For the equation \( 2s^2 + 5s = 3 \), rearranging it leads to \( 2s^2 + 5s - 3 = 0 \), then dividing by 2 prepares it for completing the square.
**Step 2: Completing the Square**
Half of the coefficient of \( s \) is determined and squared. This square, when added and subtracted ingeniously, enables the left side of the equation to factor into a perfect square trinomial, expressed as \( (s + \frac{5}{4})^2 \), streamlining the path towards the solution.
**Step 3: Isolating and Solving**
Finally, isolate the square on one side and solve by taking the square root. This provides potential solutions for \( s \) through simple arithmetic, leading to both possible solutions for the variable.
This method is detailed and logical, offering a robust toolset to tackle quadratic equations.
Solving Quadratic Equations
Completing the square is a precise method to solve quadratic equations. It transforms any quadratic into a format that is easy to solve. Here’s how it benefits the problem-solving process:
This technique rewrites the quadratic equation into the "vertex form," \((x - p)^2 = q\), where the variable \( x \) is isolated after employing the square root method. This approach ensures that all potential solutions for the quadratic are accounted for clearly and efficiently. Here's why it's powerful:
This technique rewrites the quadratic equation into the "vertex form," \((x - p)^2 = q\), where the variable \( x \) is isolated after employing the square root method. This approach ensures that all potential solutions for the quadratic are accounted for clearly and efficiently. Here's why it's powerful:
- Simplifies complex quadratics, making them easier to manipulate.
- Provides an alternative when factoring is not straightforward.
- Gives insight into the properties of the parabola, such as the vertex.