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3.2. Example 2: Solve 2𝑥² − 8𝑥 + 6 ≥ 0
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Welcome, everyone! Today, we'll be diving into quadratic inequalities, which let us determine ranges of values rather than exact ones. Can anyone remind me what a quadratic equation looks like?
Is it in the form of ax² + bx + c = 0?
Absolutely! Now, a quadratic inequality involves a similar expression but includes an inequality sign. Can someone explain why this might be useful in real life?
It helps model situations where we need to find feasible regions, like maximum heights or profit thresholds.
Exactly! Understanding these allows us to solve practical problems. Let's move into solving them step by step.
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The first step in solving our inequality is to rearrange it into standard form. Can someone tell me what that would look like for our inequality?
It would be 2x² − 8x + 6 ≥ 0.
Correct! Now, what do we do next?
We need to find the roots of the quadratic equation by solving 2x² − 8x + 6 = 0!
Great! So how can we find those roots?
We can either factor it or use the quadratic formula.
Right again! Let's use the quadratic formula for our example. Can anyone recall how it's expressed?
It's x = [-b ± √(b² - 4ac)] / 2a.
Exactly! Plugging in our values, what do we get?
We get x = 1 and x = 3.
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Create a free accountNow that we have our roots at x = 1 and x = 3, these divide our number line into intervals. What are those intervals?
The intervals are x < 1, 1 < x < 3, and x > 3.
Exactly! Let's test these intervals. Who can suggest a test point for x < 1?
We could try x = 0.
Perfect! Now, what do we find when we plug that into our expression?
It equals 6, which is valid.
Right! Now how about an interval between the roots, like x = 2?
I think it would equal -2, so that’s not valid.
Great analysis! Lastly, what about testing for x > 3?
If we use x = 4, we get 6, which is valid again.
Fantastic! So, what’s our final answer for the inequality?
x ≤ 1 or x ≥ 3!
Overview
Short Summary
This section provides a detailed method for solving the quadratic inequality 2x² − 8x + 6 ≥ 0.
Medium Summary
The section outlines a systematic approach to solving the quadratic inequality by factoring or using the quadratic formula, testing intervals, and determining where the inequality holds true. It also emphasizes the importance of graphical representation and real-world applications of quadratic inequalities.
Detailed Summary
Detailed Summary
In this section, we focus on solving a specific quadratic inequality, 2𝑥² − 8𝑥 + 6 ≥ 0. This requires a thorough understanding of the steps involved in addressing quadratic inequalities, which include:
- Standardizing the Inequality: Move all terms to one side to achieve the form 2𝑥² − 8𝑥 + 6 ≥ 0.
- Finding Roots: Solve the corresponding quadratic equation 2𝑥² − 8𝑥 + 6 = 0 using factoring or the quadratic formula. The roots found will help in dividing the number line into testable intervals.
- Sign Analysis: Analyze the signs of the quadratic expression in the intervals determined by the roots. This step helps in identifying where the inequality holds true.
- Final Solution: Compile the results using interval notation, including endpoints only if the inequality is non-strict (≥).
Additionally, the section highlights the graphical representation of the quadratic function, emphasizing the importance of understanding how the parabola interacts with the x-axis in relation to the inequality.
Audio Book
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Create a free account−(−8)±√(−8)² −4(2)(6) 8±√64−48 8±√16 8±4 𝑥 = = = = ⇒ 𝑥 = 1,3 2(2) 4 4 4
Detailed Explanation
In this step, we need to find the roots of the quadratic expression 2𝑥² − 8𝑥 + 6. We can either factor the expression or use the quadratic formula. Here, the quadratic formula is applied because it is a reliable method. First, we identify the coefficients: a = 2, b = -8, and c = 6. We then compute the discriminant (b² - 4ac) to check if there are real roots. In this case, we find the roots to be x = 1 and x = 3.
Examples & Analogies
Imagine you are trying to find the points where a ball thrown up in the air will be at a certain height. Using the quadratic formula is similar to using a precise measuring tool—it's reliable and ensures you find the heights where the ball intersects that point.
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Create a free account• 𝑥 < 1: Choose 𝑥 = 0: expression = 2(0)² − 8(0) + 6 = 6 → valid • 1 < 𝑥 < 3: Choose 𝑥 = 2: 2(2)² − 8(2) + 6 = -2 → not valid • 𝑥 > 3: Choose 𝑥 = 4: 2(4)² − 8(4) + 6 = 6 → valid
Detailed Explanation
Next, we need to determine where the inequality 2𝑥² − 8𝑥 + 6 ≥ 0 holds true. We divide the number line into intervals based on the roots we found (1 and 3), and test points from each interval: for x < 1, we choose x = 0; for 1 < x < 3, we choose x = 2; for x > 3, we choose x = 4. We calculate the value of the quadratic expression at these test points. If the expression is greater than or equal to zero, that interval is valid.
Examples & Analogies
Think of it like testing different heights of water in a tank to see if it's at a safe level. Just like you test the water level at various points (below a certain height, within a range, and above a specific height), you assess the quadratic at different x values to find where it meets the safety requirement (curves above the x-axis).
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Create a free account✅ Final Answer: 𝑥 ≤ 1 or 𝑥 ≥ 3
Detailed Explanation
From the tests performed, we concluded that the expression is positive (≥ 0) when x is less than or equal to 1 or greater than or equal to 3. Therefore, in interval notation, the solution is written as x ∈ (-∞, 1] ∪ [3, ∞). This means the valid solutions fall outside the interval (1, 3) on the number line.
Examples & Analogies
Imagine you are considering safe zones in a park where children can play. One zone is safe for all locations up to the entrance (x ≤ 1), and another zone is from the end of the parking lot (x ≥ 3). Anywhere in between could be dangerous, but outside those bounds, it's a safe environment for playing.
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Key Concepts
Core takeaways and short definitions to help you quickly recall the key ideas from this section.
Standard Form: A quadratic inequality must be expressed in standard form as ax² + bx + c ≥ 0.
Roots of the Quadratic: Solve the equation ax² + bx + c = 0 to find roots that will help in interval testing.
Interval Testing: After finding roots, test different intervals on the number line to determine where the inequality holds.
Graphical Representation: Visualize the solution set on a graph to understand where the quadratic is above or below the x-axis.
Examples
Step-by-step examples to apply the section's ideas and test your understanding.
In Example 1, solving x² - 5x + 6 < 0 demonstrated how to factor the quadratic and test intervals. Our conclusion showed valid solutions as 2 < x < 3.
In Example 2, after solving 2𝑥² - 8𝑥 + 6 ≥ 0, we found that the solutions were x ≤ 1 and x ≥ 3 by applying the quadratic formula and performing sign analysis.
Memory Aids
Interactive tools to help you remember key concepts
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Flash Cards
Glossary
Quadratic expression
An expression of the form ax² + bx + c, where a, b, and c are constants and a ≠ 0.
Quadratic inequality
An inequality that involves a quadratic expression, typically of the form ax² + bx + c <, ≤, >, or ≥ 0.
Roots
The solutions to the quadratic equation ax² + bx + c = 0, which represent the values of x where the expression equals zero.
Sign analysis
A method used to determine the intervals where a quadratic inequality holds true by testing points in each interval.