Questions tagged [radicals]

For questions involving radical of numbers or radical of expressions (i.e. numbers/expressions raised to the power of a fraction).

A radical expression is any mathematical expression containing a radical symbol $~(√~)~$.

Many people mistakenly call this a 'square root' symbol, and many times it is used to determine the square root of a number. However, it can also be used to describe a cube root, a fourth root, or higher.

When the radical symbol is used to denote any root other than a square root, there will be a superscript number in the $'V'$-shaped part of the symbol. For example, $~3\sqrt{8}~$ means to find the cube root of $~8~$. If there is no superscript number, the radical expression is calling for the square root.

The term underneath the radical symbol is called the radicand.

Steps required for Simplifying Radicals:

Step $~1~$: Find the prime factorization of the number inside the radical. Start by dividing the number by the first prime number $~2~$ and continue dividing by $~2~$ until you get a decimal or remainder. Then divide by $~3,~ 5,~ 7,~$ etc. until the only numbers left are prime numbers. Click on the link to see some examples of Prime Factorization. Also factor any variables inside the radical.

Step $~2~$: Determine the index of the radical. The index tells you how many of a kind you need to put together to be able to move that number or variable from inside the radical to outside the radical. For example, if the index is $~2~$ (a square root), then you need two of a kind to move from inside the radical to outside the radical. If the index is $~3~$ (a cube root), then you need three of a kind to move from inside the radical to outside the radical.

Step $~3~$: Move each group of numbers or variables from inside the radical to outside the radical. If there are nor enough numbers or variables to make a group of two, three, or whatever is needed, then leave those numbers or variables inside the radical. Notice that each group of numbers or variables gets written once when they move outside the radical because they are now one group.

Step $~4~$: Simplify the expressions both inside and outside the radical by multiplying. Multiply all numbers and variables inside the radical together. Multiply all numbers and variables outside the radical together.

A closely related tag is the tag.

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How can we show that $\sqrt{a}+\sqrt{b}+\sqrt{c}$ is a rational number only if $a,b,c$ are perfect squares?

Question I saw a lot of problems that assume this: $\sqrt{a}+\sqrt{b}+\sqrt{c}$ is a rational number only if $a,b,c$ are perfect squares. I wonder how can we demonstrate it because I saw a lot of people using it. Also, can I use it without a…
IONELA BUCIU
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Why can I simplify radicals? (eg, $\sqrt{153} = \sqrt{3}\cdot \sqrt{3}\cdot \sqrt{17}$)

I know it might sound like a ridiculously easy question to answer, but I just can't put two and two together for some reason. Say for example you have: $$\sqrt{153}$$ You can break it down to $$\sqrt{3}\cdot \sqrt{3}\cdot \sqrt{17}$$ (and of…
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How can you simplify $\sqrt{9-6\sqrt{2}}$?

How do you simplify: $$\sqrt{9-6\sqrt{2}}$$ A classmate of mine changed it to $$\sqrt{9-6\sqrt{2}}=\sqrt{a^2-2ab+b^2}$$ but I'm not sure how that helps or why it helps. This questions probably too easy to be on the Math Stack Exchange but I'm not…
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If $a$ is a real number then is $\sqrt{a^2}$ equal to $a$ or plus minus $a$?

I am confused about this. $\sqrt{4}$ is $2$ or $\pm 2$? If $a \in \mathbb{C}$ then will there be the $\pm$ sign in $\sqrt{a}$? when this plus minus thing arrives?
user136782
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Simplifying Radical Expression

I came across this question in a text book while preparing for return to university. It has been a few years since I flexed the old grey matter and I have not been able to arrive at the solution. Any help would be much appreciated. The question…
user404553
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Simplifying $9^{3/4}$, I get $3\sqrt[4]{9}$, but that's not the answer. Why?

I am trying to simplify: $9^\frac{3}{4}$ So this is what I did: $9^\frac{3}{4} = \sqrt[4]{9^3}$ $\sqrt[4]{3*3*3*3*3*3}$ $3\sqrt[4]{3*3}$ $3\sqrt[4]{9}$ $3\sqrt[4]{3^2}$ I don't see how I can simplify this even more, however the answer I provided is…
Pablo
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express the value of an expression as a common factor

In the following problem, by adding $0.141414$..., $0.414141..., 0.151515...$, and $0.515151...$, I get $1.111....$ Then the expression becomes square root ($11 \times 1.1111$....). My answer is $11 \times \sqrt{0.1010101...}$, which is different…
user321527
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Given the nth root of m, what are n and m called?

Very simple question: In dividing, you have the quotient, dividend, and divisor. When you have the $n$th root of $m$, what are the names of $n$ and $m$?
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is $\sqrt{x}$ always positive?

I recently saw someone say: $\sqrt{x}$ is, by definition, positive Which didn't sit easily with me as we always say $\pm$ for any square root. Then it got me thinking that if, by definition, the symbol $\sqrt{x}$ meant the positive or the negative…
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Why doesn't $\sqrt {x^3} = x \sqrt {x}$

According to the law of radicals: $$ \sqrt {an} = \sqrt a \cdot \sqrt n $$ Wouldn't it make sense that: $\sqrt {x^3}= \sqrt {x^2} \cdot \sqrt x = x \sqrt x$ Obviously this doesn't work if you plug in values and compare, but this makes logical sense?
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Which mixed numbers have the property $\sqrt{n + \frac{p}{q}}=n\sqrt{\frac{p}{q}}$?

Could I please have help with describing mixed numbers (aka mixed fractions) that have this property: Show that $\sqrt{9\frac{9}{80}}=9\sqrt{\frac{9}{80}}$ and $\sqrt{4\frac{4}{15}}=4\sqrt{\frac{4}{15}},\;$ where $\sqrt{9\frac{9}{80}} =…
PlsHelpMe
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Convert $8 {\sqrt 2}$ to $ \frac{16} {\sqrt 2}$

Can anyone please explain to me how this happens!? My brain cannot think how to get from one to the other. Thanks! $8 {\sqrt 2}$ to $ \frac{16} {\sqrt 2}$
Dani
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Square root of a square

I'm little puzzled with square roots basics which says that square root of a squared number is absolute value of that number. I was in a impression that it would have both positive and negative roots.For example The Basic says: $\sqrt{2^2} = |2| =…
vikram
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Number of irrational roots

I know that a number will have 2 square roots, 3 cube roots, and so on. This seems easy to extend to rational roots: e.g. There will be 3 2/3 roots. But what about irrational roots? How many roots are there to e.g. $3^{1/\pi}$? Is there a general…
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What is the solution for $x+22=-6\sqrt{2x+9}$

So, I want to solve for x in the radical equation: $x + 22 = -6\sqrt{2x+9}$ By Squaring each expression we get: $(x + 22)^2 = (-6\sqrt{2x+9})^2$ $ x^2 + 44x + 484 = 36\cdot(2x+ 9) $ $ x^2 + 44x + 484 = 72x + 324 $ Now by solving the quadratic…
Robario
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