Chapter 11: Problem 14
Solve. $$ t^{2}+4 t=1 $$
Short Answer
Expert verified
The solutions are \( t = -2 + \, \text{√5} \) and \( t = -2 - \, \text{√5} \).
Step by step solution
01
Move the Constant Term to the Left Side
Begin by re-arranging the equation to set it to zero. Subtract 1 from both sides:\[ t^2 + 4t - 1 = 0 \]
02
Apply the Quadratic Formula
To solve for \(t\), use the quadratic formula \( t = \frac{{-b \, \text{±} \, \sqrt{{b^2 - 4ac}}}}{{2a}} \). Here, \(a = 1\), \(b = 4\), and \(c = -1\).
03
Calculate the Discriminant
First, calculate the discriminant, \( \, \text{Δ} = b^2 - 4ac \):\[ \, \text{Δ} = 4^2 - 4 \times 1 \times (-1) = 16 + 4 = 20 \]
04
Find the Square Root of the Discriminant
Compute the square root of the discriminant:\[ \, \text{√20} = 2 \, \text{√5} \]
05
Substitute Back into the Quadratic Formula
Substitute \(b = 4\), \( \, \text{√20} = 2 \, \text{√5} \) back into the quadratic formula:\[ t = \frac{{-4 \, \text{±} \, 2 \, \text{√5}}}{2} \]
06
Simplify the Expression
Simplify the fraction:\[ t = -2 \, \text{±} \, \text{√5} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic formula
To solve any quadratic equation of the form \(ax^2 + bx + c = 0\), we can use the quadratic formula. This formula is given by:
\(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)
This formula helps us find the roots (solutions) of the quadratic equation.
Here’s a breakdown of the parts:
\(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)
This formula helps us find the roots (solutions) of the quadratic equation.
Here’s a breakdown of the parts:
- a, b, and c: The coefficients of the equation where \(a\) is the coefficient of \(x^2\), \(b\) is the coefficient of \(x\), and \(c\) is the constant term.
- Discriminant (\(\Delta\)): This part is inside the square root: \(b^2 - 4ac\). It tells us about the nature of the roots.
- \( \pm \) symbol: This means there are typically two solutions, one with addition and one with subtraction.
discriminant
The discriminant is a key part of the quadratic formula. It is given by \(b^2 - 4ac\) and is denoted by the symbol \( \Delta\).
The value of the discriminant determines the nature of the roots:
In the given exercise, the discriminant \( \Delta = 20\) was calculated using: \( - 4ac = 16 + 4 = 20\). Since \( \Delta > 0\), it indicates two real and distinct solutions.
The value of the discriminant determines the nature of the roots:
- If \( \Delta > 0\): There are two real and distinct roots.
- If \( \Delta = 0\): There is exactly one real root (also called a repeated or double root).
- If \( \Delta < 0\): There are two complex roots (they are not real numbers).
In the given exercise, the discriminant \( \Delta = 20\) was calculated using: \( - 4ac = 16 + 4 = 20\). Since \( \Delta > 0\), it indicates two real and distinct solutions.
simplification steps
Simplification steps are final adjustments to make sure the equation is easily interpreted. This includes:
In the exercise, the simplified form of the quadratic equation solution was: \( t = -2 \pm \sqrt{5}\)
Here’s a more detailed breakdown of the simplification steps:
After substituting the discriminant back into the quadratic formula:
\( t = \frac{-4 \pm 2\sqrt{5}}{2} \)
We then simplify the fraction by dividing the numerator terms by the denominator:
\( t = -2 \pm \sqrt{5}\))
This final step ensures we have the simplest form of the solutions.
- Combining like terms
- Reducing fractions
- Making sure the solutions are in their simplest form
In the exercise, the simplified form of the quadratic equation solution was: \( t = -2 \pm \sqrt{5}\)
Here’s a more detailed breakdown of the simplification steps:
After substituting the discriminant back into the quadratic formula:
\( t = \frac{-4 \pm 2\sqrt{5}}{2} \)
We then simplify the fraction by dividing the numerator terms by the denominator:
\( t = -2 \pm \sqrt{5}\))
This final step ensures we have the simplest form of the solutions.