Chapter 6: Problem 81
Solve each equation. $$ 3 y^{2}-14 y-5=0 $$
Short Answer
Expert verified
The solutions are \( y = 5 \) and \( y = -\frac{1}{3} \).
Step by step solution
01
Identify the type of equation
The given equation is a quadratic equation in the form \(ax^2 + bx + c = 0\). Here, \(a = 3\), \(b = -14\), and \(c = -5\).
02
Apply the quadratic formula
The quadratic formula is \( y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \). We will use this formula to solve for \(y\).
03
Calculate the discriminant
The discriminant is given by \( b^2 - 4ac \). Substitute the values: \((-14)^2 - 4 \cdot 3 \cdot (-5) = 196 + 60 = 256\). The discriminant is 256.
04
Evaluate the expression under the square root
Since the discriminant is 256, calculate \( \sqrt{256} = 16 \).
05
Solve for the two possible values of y
Substitute \( b = -14 \), \( \sqrt{256} = 16 \), and \( a = 3 \) into the quadratic formula: 1. \( y = \frac{-(-14) + 16}{2 \times 3} = \frac{14 + 16}{6} = \frac{30}{6} = 5 \) 2. \( y = \frac{-(-14) - 16}{2 \times 3} = \frac{14 - 16}{6} = \frac{-2}{6} = -\frac{1}{3} \)
06
State the solutions
The solutions to the equation are \( y = 5 \) and \( y = -\frac{1}{3} \).
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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 crucial tool for solving quadratic equations. A quadratic equation typically takes the form: \[ ax^2 + bx + c = 0 \] where \( a \), \( b \), and \( c \) are constants, and \( a eq 0 \). To find the solutions for \( x \), we employ the quadratic formula:\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] This formula enables us to find the roots of the equation by allowing us to calculate both possible solutions efficiently.
- "\(-b\)" becomes the opposite of \( b \).
- "\(\pm\)" indicates there are usually two solutions: one where you add the square root, and another where you subtract.
- The value under the square root - "\(b^2 - 4ac\)" - is called the discriminant.
Discriminant
The discriminant is a component of the quadratic formula represented by the expression \( b^2 - 4ac \). It plays a significant role in determining the nature of the roots of a quadratic equation. Here's what the discriminant can tell us:
- If \( b^2 - 4ac > 0 \), there are two distinct real solutions. This indicates that the parabola crosses the x-axis at two points.
- If \( b^2 - 4ac = 0 \), there is exactly one real solution. The parabola touches the x-axis at exactly one point, resulting in a "double root".
- If \( b^2 - 4ac < 0 \), there are no real solutions, meaning the parabola does not intersect the x-axis.
Solving Quadratic Equations
Solving quadratic equations becomes much easier by understanding and applying both the quadratic formula and the discriminant. Here's a quick guide to solving these equations:1. **Identify the equation type.**
In a typical scenario, you have \( ax^2 + bx + c = 0 \). Recognize your constants \( a \), \( b \), and \( c \) from your equation. 2. **Calculate the discriminant.**
Use \( b^2 - 4ac \) to assess the roots' nature and number. This step precludes deeper calculation if no real roots exist. 3. **Apply the quadratic formula.**
Insert \( a \), \( b \), and \( c \) into: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Compute the values for \( x \) for both \( +\sqrt{} \) and \( -\sqrt{} \) scenarios to find the two solutions.In our example, when we calculated step-by-step for \( y \), we obtained the solutions \( y = 5 \) and \( y = -\frac{1}{3} \). The use of these steps can systematically solve similar quadratic equations you face in your studies.
In a typical scenario, you have \( ax^2 + bx + c = 0 \). Recognize your constants \( a \), \( b \), and \( c \) from your equation. 2. **Calculate the discriminant.**
Use \( b^2 - 4ac \) to assess the roots' nature and number. This step precludes deeper calculation if no real roots exist. 3. **Apply the quadratic formula.**
Insert \( a \), \( b \), and \( c \) into: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] Compute the values for \( x \) for both \( +\sqrt{} \) and \( -\sqrt{} \) scenarios to find the two solutions.In our example, when we calculated step-by-step for \( y \), we obtained the solutions \( y = 5 \) and \( y = -\frac{1}{3} \). The use of these steps can systematically solve similar quadratic equations you face in your studies.