Inequality question -- Need help getting started...

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In summary: Amen! Mathematics is very cumulative. Anything that you were taught earlier will be used over and over in what follows. It can be very beneficial to review earlier material until it becomes natural to you.
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Homework Statement
Please see below
Relevant Equations
Please see below
For this,
1679620253187.png

I am confused how to show that they are equivalent. Can some please give me some guidance?

Many thanks!
 
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  • #2
What is always the first step when absolute values are involved? Two cases for |x-a|, depending on the sign of x-a.
Where can you go from there?
 
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  • #3
FactChecker said:
What is always the first step when absolute values are involved? Two cases for |x-a|, depending on the sign of x-a.
Where can you go from there?
Thanks for your reply @FactChecker!

First case is

-(x - a)

Second case is

x - a
 
  • #4
Right. Now you need to show some work using that.
 
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  • #5
FactChecker said:
Right. Now you need to show some work using that.
Thanks @FactChecker!

##0 < -(x - a) < \delta##
##0 < x - a <\delta##

Many thanks!
 
  • #6
Callumnc1 said:
Thanks @FactChecker!

##0 < -(x - a) < \delta##
##0 < x - a <\delta##

Many thanks!
Nevermind, I understand now. It seems so strange that you can multiply all three sides of an equality by the same number. I don't know what this property is called thought.
 
  • #7
Callumnc1 said:
I am confused how to show that they are equivalent. Can some please give me some guidance?
For the continued inequality ##0 < |x - a| < \delta##, it's helpful to draw a sketch or two of the number line with a in an arbitrary position. x will then have to be somewhere inside a band of width ##2\delta## around a, but excluding a itself.
Callumnc1 said:
Nevermind, I understand now. It seems so strange that you can multiply all three sides of an equality by the same number. I don't know what this property is called thought.
The statement you started with is not an equation -- it's an inequality. There is a property of equations that you can multiply both sides of an equation by any nonzero number to get a new, equivalent equation. This idea can be extended to a continued equation.

There is a similar property for inequalities, but with a twist. You can multiply both sides of an inequality by a positive number to get a new, equivalent inequality. This also can be extended to continued inequalities. The twist is that if you multiply both sides by a negative number, the direction of the inequality must change.

Yet again, the very large gaps in your mathematical background are causing you to spend a lot of time merely trying to understand what would be immediately obvious to someone who didn't have these gaps.
 
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Mark44 said:
Yet again, the very large gaps in your mathematical background are causing you to spend a lot of time merely trying to understand what would be immediately obvious to someone who didn't have these gaps.
Amen! Mathematics is very cumulative. Anything that you were taught earlier will be used over and over in what follows. It can be very beneficial to review earlier material until it becomes natural to you.
 
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FAQ: Inequality question -- Need help getting started...

What is an inequality in mathematics?

An inequality is a mathematical statement that compares two expressions and shows that one is greater than, less than, greater than or equal to, or less than or equal to the other. It uses symbols like >, <, ≥, and ≤.

How do you solve a linear inequality?

To solve a linear inequality, you follow similar steps as solving a linear equation: isolate the variable on one side of the inequality sign. However, if you multiply or divide both sides by a negative number, you must reverse the inequality sign.

What are the different types of inequalities?

The different types of inequalities include linear inequalities, polynomial inequalities, rational inequalities, and absolute value inequalities. Each type involves different methods and rules for solving.

Can you provide an example of solving an inequality?

Sure! Consider the inequality 2x - 3 < 7. To solve it, add 3 to both sides to get 2x < 10. Then, divide both sides by 2 to get x < 5. So, the solution is x < 5.

What does it mean to graph an inequality?

Graphing an inequality means representing its solutions on a number line or coordinate plane. For a number line, you use open or closed circles to indicate whether endpoints are included. For a coordinate plane, you shade the region that represents all the solutions.

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