Chapter 11: Problem 50
Solve. Use a calculator to approximate, to three decimal places, the solutions as rational numbers. $$ 3 x^{2}-3 x-2=0 $$
Short Answer
Expert verified
\[x \approx 1.550\] and \[x \approx -0.217\].
Step by step solution
01
- Identify the quadratic equation
The given equation is a quadratic equation in the form of \[ax^2 + bx + c = 0\] where \[a = 3\], \[b = -3\], and \[c = -2\].
02
- Use the quadratic formula
The quadratic formula is \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\]. Substitute the values of \[a\], \[b\], and \[c\] into the formula.
03
- Calculate the discriminant
Substitute \[a = 3\], \[b = -3\], and \[c = -2\] into the discriminant formula \[b^2 - 4ac\]:\[(-3)^2 - 4(3)(-2)\].Simplify to: \[9 + 24 = 33\].
04
- Simplify the quadratic formula
Using the discriminant \[33\], proceed with the quadratic formula:\[x = \frac{-(-3) \pm \sqrt{33}}{2(3)}\] simplifies to \[x = \frac{3 \pm \sqrt{33}}{6}\].
05
- Calculate the roots
Calculate the approximate solutions using a calculator:\[x_1 = \frac{3 + \sqrt{33}}{6} \approx 1.550\]\[x_2 = \frac{3 - \sqrt{33}}{6} \approx -0.217\].
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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 for solving quadratic equations of the form \( ax^2 + bx + c = 0 \).
It helps find the values of \( x \) that satisfy the equation. The formula is expressed as follows:
\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
Here’s what each part means:
Make sure to substitute the values of \( a, b, \) and \( c \) carefully to find accurate solutions.
It helps find the values of \( x \) that satisfy the equation. The formula is expressed as follows:
\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]
Here’s what each part means:
- \textbf{\( a \):} The coefficient of \( x^2 \)
- \textbf{\( b \):} The coefficient of \( x \)
- \textbf{\( c \):} The constant term
Make sure to substitute the values of \( a, b, \) and \( c \) carefully to find accurate solutions.
discriminant
The discriminant is a specific part of the quadratic formula. It’s the expression inside the square root: \( b^2 - 4ac \).
The discriminant reveals important information about the nature of the roots:
\[ (-3)^2 - 4(3)(-2) = 9 + 24 = 33 \]
Since 33 is positive, the equation \( 3x^2 - 3x - 2 = 0 \) has two distinct real roots.
The discriminant reveals important information about the nature of the roots:
- If the discriminant is positive (greater than 0), the quadratic equation has two distinct real roots.
- If the discriminant is zero, the quadratic equation has exactly one real root (a repeated root).
- If the discriminant is negative (less than 0), the quadratic equation has two complex roots.
- \textbf{\( a \) = 3}
- \textbf{\( b \) = -3}
- \textbf{\( c \) = -2}
\[ (-3)^2 - 4(3)(-2) = 9 + 24 = 33 \]
Since 33 is positive, the equation \( 3x^2 - 3x - 2 = 0 \) has two distinct real roots.
approximating roots
After finding the discriminant and using the quadratic formula, we arrive at the expression that gives the roots:
\[ x = \frac{3 \pm \sqrt{33}}{6} \]
To get the exact values of the roots, we need to handle the square root and the arithmetic.
This is often done with a calculator to get precise decimal values.
The approximate roots are calculated as follows:
\[ x = \frac{3 \pm \sqrt{33}}{6} \]
To get the exact values of the roots, we need to handle the square root and the arithmetic.
This is often done with a calculator to get precise decimal values.
The approximate roots are calculated as follows:
- \textbf{First Root (\( x_1 \)):} Simplify \( \frac{3 + \sqrt{33}}{6} \). Using a calculator for the square root of 33, we find:
\[ x_1 \approx \frac{3 + 5.745}{6} \approx \frac{8.745}{6} \approx 1.550 \] - \textbf{Second Root (\( x_2 \)):} Simplify \( \frac{3 - \sqrt{33}}{6} \). Using the same square root value, we find:
\[ x_2 \approx \frac{3 - 5.745}{6} \approx \frac{-2.745}{6} \approx -0.217 \]