Chapter 3: Problem 85
Find the zeros of the function algebraically. Give exact answers. $$f(x)=4 x^{2}+3 x-3$$
Short Answer
Expert verified
The zeros of the function are \( \frac{-3 + \sqrt{57}}{8} \) and \( \frac{-3 - \sqrt{57}}{8} \).
Step by step solution
01
Identify the Quadratic Function
The given function is a quadratic function in the form of \[ f(x) = ax^2 + bx + c \]Here, identify the coefficients: \( a = 4 \), \( b = 3 \), and \( c = -3 \).
02
Apply the Quadratic Formula
The quadratic formula is given by: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]Substitute the identified coefficients \( a, b, \) and \( c \) into the formula: \( a = 4 \), \( b = 3 \), and \( c = -3 \).
03
Calculate the Discriminant
The discriminant (\( \Delta \)) is defined as \( \Delta = b^2 - 4ac \). Substitute \( a, b, \) and \( c \) into the discriminant: \[ \Delta = 3^2 - 4(4)(-3) \] \[ \Delta = 9 + 48 \] \[ \Delta = 57 \]
04
Substitute Back Into the Quadratic Formula
Using the discriminant calculated in Step 3, substitute back into the quadratic formula: \[ x = \frac{-3 \pm \sqrt{57}}{8} \].
05
Simplify the Solutions
Thus, the exact zeros of the function are: \[ x_1 = \frac{-3 + \sqrt{57}}{8} \] and \[ x_2 = \frac{-3 - \sqrt{57}}{8} \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Formula
The quadratic formula is a powerful tool used to solve any quadratic equation of the form \( ax^2 + bx + c = 0 \). Quadratic equations include terms like \(x^2\), \(x\), and a constant. The quadratic formula provides a straightforward method to find the solutions or 'roots' of these equations, which are the values of \(x\) where the equation equals zero.
The quadratic formula is: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] This formula may look a bit complex, but each part has a specific role:
The quadratic formula is: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] This formula may look a bit complex, but each part has a specific role:
- The term \(-b\) gives the opposite of the coefficient of \(x\).
- The term \(\b^2 - 4ac\) under the square root is called the discriminant.
- The \(2a\) in the denominator adjusts for the coefficient of \(x^2\).
Discriminant
The discriminant is a key part of the quadratic formula, and it tells us about the nature of the roots of the quadratic equation. The discriminant is given by the expression: \[ \Delta = b^2 - 4ac \] The value of the discriminant (\Delta) can help determine the nature of the roots:
- If \Delta > 0, there are two distinct real roots.
- If \Delta = 0, there is exactly one real root, often called a repeated or double root.
- If \Delta < 0, there are no real roots; instead, there are two complex roots.
Solving Quadratic Equations
Solving quadratic equations involves finding the values of \(x\) that make the equation equal to zero. Here's a clear step-by-step method using the quadratic formula:
- Identify the coefficients: For the equation \(4x^2 + 3x - 3 = 0\), the coefficients are \(a = 4\), \(b = 3\), and \(c = -3\).
- Calculate the discriminant: Plug these values into the discriminant formula \( \Delta = b^2 - 4ac \) to get \(\Delta = 57\).
- Substitute into the quadratic formula: Use the values of \(a\), \(b\), and \( \Delta \) in the quadratic formula \[\backslash x = \frac{-3 \pm \sqrt{57}}{8} \] to find the solutions.
- Simplify the solutions: The solutions are: \[ x_1 = \frac{-3 + \sqrt{57}}{8} \] and \[ x_2 = \frac{-3 - \sqrt{57}}{8} \].