Understanding Quadratic Inequality: Explained in Detail

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Discussion Overview

The discussion focuses on understanding quadratic inequalities, exploring their definitions, properties, and methods for solving them. Participants share various approaches, examples, and visualizations related to the topic.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant requests a detailed explanation of quadratic inequalities, expressing confusion about the topic.
  • Another participant suggests that video tutorials may assist in understanding quadratic inequalities.
  • A participant proposes finding the roots of the quadratic equation to discuss the intervals created by these roots.
  • It is noted that quadratic inequalities can take various forms, such as ax^2 + bx + c < 0 or ax^2 + bx + c >= 0.
  • One participant emphasizes that the inequality can relate to a term or value other than zero, and that manipulating the inequality can help relate it to zero.
  • A question is raised about visualizing the relationship between the graph of the quadratic and the number line, specifically regarding the intervals between intersections.
  • A participant mentions a video resource that explains how the roots of the quadratic expression divide the number line into intervals for testing truth values.
  • An example is provided involving the quadratic -4x^2 - 4x - 1, discussing the importance of reversing the inequality when dividing by a negative number and identifying critical values.
  • It is noted that the critical value found cuts the number line into two intervals, which should be tested for truth.

Areas of Agreement / Disagreement

Participants express various viewpoints and methods for understanding and solving quadratic inequalities, but no consensus is reached on a single approach or interpretation.

Contextual Notes

Some participants mention specific examples and steps in solving quadratic inequalities, but there are unresolved assumptions regarding the manipulation of inequalities and the implications of critical values.

Who May Find This Useful

This discussion may be useful for students or individuals seeking to understand quadratic inequalities, their properties, and methods for solving them.

Lim Y K
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Can someone explain to be in detail what is quadratic inequality? It's rather confusing. Thank you
 
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There are some video tutorials on it that may help:

 
Try to find the 2 roots of the quadratic equation and discuss the intervals made of these numbers.
 
What is a quadratic inequality?
ax^2+bx+c&lt;0orax^2+bx+c&lt;=0orax^2+bx+c&gt;0orax^2+bx+c&gt;=0
 
To be clearer, do not let the relation to 0 fool you. The relation can be with a term or a value other than zero on one side. Merely adding the additive inverse to both sides can bring the inequality to relate a quadratic expression to zero. Also, if the quadratic is factorable, you may be able to have something like (ax+b)(cx+d) (relation-symbol)(0).
 
ImageUploadedByPhysics Forums1445234898.698360.jpg

For visualisation's sake, is it something like that? The space between the two intersection in the graph is equivalent to the space between he two lines on the number line?
 
Lym Y K,
The Mathispower4u (which jedishru posted) video you should find very helpful in understanding what to do with solving a quadratic inequality. The roots of the quadratic expression form the x-number line into three intervals, and any value in each interval can be chosen to test the truth or falsity for the interval.
 
The example in the paper in your included photograph shows -4x^2-4x-1 and we must assume it's meant as related versus 0. You can/should DIVIDE both sides by NEGATIVE 4, and this MUST reverse the direction of the inequality symbol. Why? because multiplication or division by a negative VALUE.
That step now gives you x^2+x+1/4 versus 0, as said, with relation reversed from what it was originally. This quadratic is factorable giving you exactly ONE critical x value.

(x+1/2)^2. versus 0. (You did not show on your paper the inequality symbol relating). The critical value is at x=-1/2, just one single value, cutting the x-number line into just two intervals. Now, you test each interval, and maybe also you need to test that critical x value of -1/2.
 

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