Chapter 7: Problem 22
In Exercises \(11-30,\) solve the given quadratic equations by completing the square. Exercises \(11-14\) and \(17-20\) may be checked by factoring. $$3 x^{2}=3-4 x$$
Short Answer
Expert verified
The solutions are \(x = \frac{-2 + \sqrt{13}}{3}\) and \(x = \frac{-2 - \sqrt{13}}{3}\).
Step by step solution
01
Rearrange the Equation
First, rearrange the equation \(3x^2 = 3 - 4x\) into the standard quadratic form \(ax^2 + bx + c = 0\). Begin by moving all terms to one side of the equation, resulting in \(3x^2 + 4x - 3 = 0\).
02
Divide by the Coefficient of x²
Divide all terms by the coefficient of \(x^2\), which is 3, to simplify the equation. \(x^2 + \frac{4}{3}x = 1\).
03
Complete the Square
To complete the square, take half of the coefficient of \(x\) (which is \(\frac{4}{3}\)), square it, and add to both sides. \(\left(\frac{2}{3}\right)^2 = \frac{4}{9}\). Add \(\frac{4}{9}\) to both sides: \(x^2 + \frac{4}{3}x + \frac{4}{9} = 1 + \frac{4}{9}\).
04
Simplify and Factor
The left side of the equation now is a perfect square trinomial, so factor it: \((x + \frac{2}{3})^2\). Simplify the right side: \(\frac{9}{9} + \frac{4}{9} = \frac{13}{9}\). Thus, \((x + \frac{2}{3})^2 = \frac{13}{9}\).
05
Solve for x
Take the square root of both sides: \(x + \frac{2}{3} = \pm\sqrt{\frac{13}{9}}\). This gives \(x + \frac{2}{3} = \pm\frac{\sqrt{13}}{3}\). Next, solve for \(x\) by subtracting \(\frac{2}{3}\) from both sides: \(x = -\frac{2}{3} \pm \frac{\sqrt{13}}{3}\). Thus, the solutions are \(x = \frac{-2 + \sqrt{13}}{3}\) and \(x = \frac{-2 - \sqrt{13}}{3}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Completing the Square
Completing the square is a technique used to solve quadratic equations, particularly when factoring is difficult or impossible. This method transforms a quadratic equation into a perfect square trinomial.
To complete the square:
To complete the square:
- Start by rearranging the equation into the form: \(ax^2 + bx = c\).
- Take the coefficient of \(x\), divide it by 2, and then square it. This value is added to both sides of the equation.
- This process converts the left side into a perfect square trinomial, which can be factored into a binomial squared, such as \((x + rac{b}{2a})^2\).
- Solve the resulting equation by isolating the variable \(x\).
Factoring
Factoring is a quick and efficient way to solve quadratic equations, especially when the equation can be easily expressed as a product of binomials. This method relies heavily on identifying two numbers that add up to the coefficient of \(x\) and multiply to the constant term.
To factor a quadratic equation:
To factor a quadratic equation:
- Ensure that the equation is in standard quadratic form, \(ax^2 + bx + c = 0\).
- Look for two numbers that multiply to \('ac'\) and add to \(b\).
- Once found, rewrite the middle term using these two numbers.
- Factor by grouping or directly factor into two binomials.
Solving Quadratic Equations
Solving quadratic equations involves finding the values of \(x\) that satisfy the equation \(ax^2 + bx + c = 0\). Several methods are available, such as factoring, completing the square, and using the quadratic formula.
To solve a quadratic equation:
To solve a quadratic equation:
- Try factoring first if it's possible, as it provides the quickest solution.
- If factoring doesn't work, use the completing the square method to reformat the equation into a solvable form.
- The quadratic formula, \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\), offers a foolproof solution for any quadratic equation.
Standard Quadratic Form
The standard quadratic form is the foundation of all quadratic equations and is written as \(ax^2 + bx + c = 0\), with \(a\), \(b\), and \(c\) being constants where \(a \eq 0\).
- This form is crucial because it dictates the methods used for solving the equation.
- It provides a clear structure for identifying the coefficients required for various solving techniques, such as the quadratic formula or completing the square.
- Rewriting any given quadratic equation into this form is often the first step in the solving process, ensuring consistency and accuracy while applying algebraic methods.