Chapter 11: Problem 39
Let \(g(x)=4 x^{2}-2 x-3 .\) Find \(x\) such that \(g(x)=0\)
Short Answer
Expert verified
The solutions are \( x = \frac{1 + \sqrt{13}}{4} \) and \( x = \frac{1 - \sqrt{13}}{4} \).
Step by step solution
01
- Write down the equation
Start by writing down the given equation: \[ g(x) = 4x^2 - 2x - 3 \]Given: \( g(x) = 0 \)
02
- Set the equation to zero
Since we want to find \( x \) such that \( g(x) = 0 \), set the equation equal to zero: \[ 4x^2 - 2x - 3 = 0 \]
03
- Apply the quadratic formula
To solve for \( x \) in the quadratic equation \( 4x^2 - 2x - 3 = 0 \), use the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]For our equation, \( a = 4 \), \( b = -2 \), and \( c = -3 \).
04
- Solve for the discriminant
Calculate the discriminant \( \Delta \) using the formula \[ \Delta = b^2 - 4ac \]: \[ \Delta = (-2)^2 - 4 \cdot 4 \cdot (-3) \]\[ \Delta = 4 + 48 \]\[ \Delta = 52 \]
05
- Compute the solutions
Substitute the discriminant \( \Delta \) and the constants \( a \) and \( b \) back into the quadratic formula to find the solutions: \[ x = \frac{-(-2) \pm \sqrt{52}}{2 \cdot 4} \]\[ x = \frac{2 \pm \sqrt{52}}{8} \]\[ x = \frac{2 \pm 2\sqrt{13}}{8} \]\[ x = \frac{1 \pm \sqrt{13}}{4} \]
06
- Present the final answers
Thus, the solutions for \( x \) are: \[ x = \frac{1 + \sqrt{13}}{4} \]and\[ x = \frac{1 - \sqrt{13}}{4} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic formula
To solve quadratic equations like the one given (4x^2 - 2x - 3 = 0), the quadratic formula is an essential tool. The quadratic formula allows us to find the roots of any quadratic equation in the form ax^2 + bx + c = 0. The formula is:
\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
This formula might look complex initially, but it breaks down into manageable parts:
\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
This formula might look complex initially, but it breaks down into manageable parts:
- -b: The opposite of the coefficient of x
- \pm: Plus or minus, indicating two potential solutions
- \sqrt{b^2 - 4ac}: The square root of the discriminant, which we'll discuss next
- 2a: Twice the coefficient of or the squared term
discriminant
The discriminant is a crucial part of the quadratic formula, represented by \( b^2 - 4ac \), and it helps determine the nature of the roots without fully solving the equation. We compute the discriminant as follows:
\[ \Delta = b^2 - 4ac \]
Depending on the value of \( \Delta \):
\( \Delta = 52 \)
Since \( 52 > 0 \), we can confidently say there are two distinct real roots for the equation 4x^2 - 2x - 3 = 0.
\[ \Delta = b^2 - 4ac \]
Depending on the value of \( \Delta \):
- If \( \Delta > 0 \), there are two distinct real roots
- If \( \Delta = 0 \), there is exactly one real root or a repeated root
- If \( \Delta < 0 \), there are no real roots, but two complex roots
\( \Delta = 52 \)
Since \( 52 > 0 \), we can confidently say there are two distinct real roots for the equation 4x^2 - 2x - 3 = 0.
roots of quadratic equations
Finding the roots of a quadratic equation means identifying the values of x that make the equation (ax^2 + bx + c = 0) true. These roots can be found using the quadratic formula, factoring, or completing the square. In this exercise, we use the quadratic formula due to its general applicability.
Given:\[ x = \frac{1\pm \sqrt{13}}{4} \]
This breaks down to two solutions:
Given:\[ x = \frac{1\pm \sqrt{13}}{4} \]
This breaks down to two solutions:
- \( x = \frac{1 + \sqrt{13}}{4} \) - a positive root
- \( x = \frac{1 - \sqrt{13}}{4} \) - a negative root