How to Prove the Triangle Inequality ||x|| - ||y|| ≤ ||x-y||?

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    Inequality
In summary, an inequality is a mathematical statement that compares the values of two quantities. To solve an inequality, algebraic techniques such as adding, subtracting, multiplying, and dividing can be used. The main difference between solving an equation and solving an inequality is the presence of an inequality sign in the latter. There are different types of inequalities, including linear, quadratic, and rational inequalities. Inequalities have various real-life applications, such as determining eligibility for loans, comparing prices, and analyzing data in fields like economics, medicine, and engineering. They can also be used to model and solve problems in different areas of science, such as physics, chemistry, and biology.
  • #1
florenti
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Help me to show this inequality ?

Hi,

I have to show this inequality

| ||x||-||y|| | <= ||x-y||

I have tried to use the Couchy-Schwarz inequality but I didn't get anything.

Could anyone help me solving this.

Thanks a lot.

florent
 
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  • #2


The Cauchy-Schwarz inequality says that [itex]||x+ y||\le ||x||+ ||y||[/itex].

If you let x= a-b and y= b, that becomes [itex]||a-b+b||\le ||a- b||+ ||b||[/itex] or [itex]||a||\le ||a- b|+ ||b||[/itex] which, subtracting [itex]||b||[/itex] from both sides, gives [itex]||a||- ||b||\le ||a- b||[/itex]. You Should be able to use that.
 
  • #3


Thanks a lot
 

1. What is an inequality?

An inequality is a mathematical statement that compares the values of two quantities, showing which one is greater than, less than, or equal to the other.

2. How do I solve an inequality?

To solve an inequality, you can use algebraic techniques such as adding, subtracting, multiplying, and dividing both sides of the inequality by the same number. You may also need to use the properties of inequalities, such as switching the direction of the inequality when multiplying or dividing by a negative number.

3. What is the difference between solving an equation and solving an inequality?

The main difference between solving an equation and solving an inequality is that an equation has an equal sign, while an inequality has an inequality sign (such as <, >, ≤, or ≥). When solving an equation, the goal is to find the value of the variable that makes the equation true, while when solving an inequality, the goal is to find the range of values that make the inequality true.

4. What are the different types of inequalities?

There are several types of inequalities, including linear inequalities (where the variable has a power of 1), quadratic inequalities (where the variable has a power of 2), and rational inequalities (where the variable appears in the denominator of a fraction). Inequalities can also involve multiple variables and can be solved using graphs or systems of equations.

5. How can I use inequalities in real life?

Inequalities are used in a wide range of real-life situations, such as determining whether a person is eligible for a loan based on their income, comparing prices to find the best deal, and analyzing data in fields such as economics, medicine, and engineering. Inequalities can also be used to model and solve problems in various areas of science, including physics, chemistry, and biology.

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