Simplifying square root of an irrational

In summary, the conversation discusses finding a solution for the expression [(3 - 51/2)/2]1/2. The suggested approach involves rationalizing the expression and using the form of (a-b)^2 to simplify it. After some back and forth, the solution is found to be √(6-2√5) ÷ 2.
  • #1
erisedk
374
7

Homework Statement


Find [(3 - 51/2)/2]1/2

Homework Equations

The Attempt at a Solution


My calculator says (-1 + √5)/2
I have no idea how. Rationalising doesn't really do much good. Just tell me where to start.
 
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  • #2
Multiplying the original expression with ##\sqrt{2}/\sqrt{2}## will give you ##\sqrt{6-2\sqrt{5}}## in the numerator. Then think of the terms under the radical as having the form of ##(a-b)^2 = a^2-2ab+b^2##.
 
  • #3
Could you please elaborate? I'm not getting anywhere. I assume you mean use something like completing the square but I can't do it.
 
  • #4
What do you get after multiplying the original expression with ##\frac{\sqrt{2}}{\sqrt{2}}##?
 
  • #5
You could also try working the other direction. Find the square of ##\frac{-1 + \sqrt 5}{2}## and see how it simplifies.
 
  • #6
blue_leaf77 said:
What do you get after multiplying the original expression with ##\frac{\sqrt{2}}{\sqrt{2}}##?

Oh I got that, ie √(6-2√5) ÷ 2
I don't get what I'm supposed to do after this.
 
  • #7
erisedk said:
√(6-√5) ÷ 2
It is √(6-2√5) ÷ 2. Then express the terms under the radical in the form I wrote in post #2, that is, write ##6-2√5 = a^2+b^2-2ab## . FInd the right pair of ##a## and ##b## such that the LHS is equal to RHS.
 
  • #8
Got it! Thanks!
 

1. What is an irrational number?

An irrational number is a real number that cannot be expressed as a simple fraction or ratio of two integers. Examples of irrational numbers include pi (3.14159...) and the square root of 2 (1.41421...).

2. How do you simplify a square root of an irrational number?

To simplify a square root of an irrational number, you must find a perfect square factor of the number inside the square root. Then, you can take the square root of that factor and move it outside of the square root symbol.

3. Can you simplify all square roots of irrational numbers?

No, not all square roots of irrational numbers can be simplified. Only those that have perfect square factors can be simplified. For example, the square root of 7 cannot be simplified because 7 does not have any perfect square factors.

4. What is the purpose of simplifying a square root of an irrational number?

The purpose of simplifying a square root of an irrational number is to make it easier to work with and understand. Simplifying allows us to express an irrational number in a more concise and manageable form.

5. How do you know if a square root of an irrational number is simplified?

A square root of an irrational number is simplified when there are no perfect square factors left inside the square root symbol. This means that the number cannot be further simplified and is in its simplest form.

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