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.

3729 questions
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Square root positive/negative

What is the square root of $9$? Is it always $\pm 3$ or just positive $3$? Trying to find the solution set of this equation : $x-3 = \sqrt{x+3}$ I want to understand the concept of square root to solve the problem. Thanks
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Squared Square Root confusion

I am confused about the following: $$\sqrt{x^2}=?\ (\sqrt x)^2 =?\ x^{2/2}$$ The source of confusion is: Let $$f(x)=\sqrt {x^2}$$ $$g(x)=\ (\sqrt x)^2 $$ Then $$f(-3)=3$$ $$g(-3)=\mbox{undefined}?$$ While the range of $f(x)$ and $g(x)$ might be the…
S.Q
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How to solve this infinite radical

$$\sqrt{1+\sqrt{2+\sqrt{3+\sqrt{4+\sqrt{5+\sqrt{ \dots }}}}}}$$ I don't understand how to solve that. I mean I don't know where to begin. Tell me if this infinite radical has a solution or converge to a number. Thanks.
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If$ \sqrt{x^2}=|x|$, then why does $\sqrt{x^6}=x^3$ and not $|x^3|$?

Since $\sqrt{x^6}=\sqrt{(x^3)^2}$, wouldn't $\sqrt{(x^3)^2}=|x^3|$?
Allison
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why does calculators consider the negative value of the square root as an imaginary part?

when I was asked by a friend to solve this problem 0.5x = sqrt(4-3x) + 2 I got the answers -4 and 0, but when he plugged them in he said that my values were incorrect, and that's true if he took the positive values of the root function, but if he…
adib
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When is a radical in its simplest form? Seemingly conflicting answers

Simply put, is a radical in its simplest form if all square factors are removed and radicand is still a (non-square) fraction? Like: $$\frac{1}{42}\sqrt\frac{1}{2}$$ This is the solution given on Khan Academy asking to simplify the below…
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finding square root

I want to know how to find the square root/cube root of a number ending with zero. For instance, $\sqrt{1024}$ : though it's a perfect square, there is a shortcut. Like wise how can I find the $\sqrt{2240}$ or any number ending with zero? Thanks in…
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Numbers with both 3rd and 7th radical integers

I was wondering if there are any Numbers where both the 3rd radical and the 7th radical are integers. For example: 3rd radical of 125 is 5 (integer) 7th radical of 125 is 1.9932.. (no integer) I didn't find any numbers where both radicals are…
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What would happen if $\sqrt{}$ instead meant the negative square root?

I read that it is only by convention that $\sqrt{}$ means “the positive square root of”. The downvotes and user 'Thomas' 's answer compel me to clarify that I asked this hypothetical question only because of curiosity, not because of any desire to…
user53259
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Solve for x (radicals)

Solve this equation for x $ \sqrt[3]{\sqrt{x}+3} + \sqrt[3]{13-\sqrt{x}} = 4 $ I tried to put a condition for x to be $ \ge 0 $ but then do I need to cube the expressions or what?
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Solving Equations with radical Exponents

The question is $22= 2 + 5(5m - 11)^{1/2}$ so to try to solve this I first subtracted 2 and than divided by 5. than you get $4 = (5 m - 11)^{1/2}$ $$4 = \sqrt{5 m -11}$$ so$$16= 5m -11$$ or $$16+11=5m$$ or $$27 = 5 m$$ This cannot work
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Simplify numerical radical expressions with multiple terms

I'm trying to solve: $$\frac{\sqrt 6}{\sqrt7} \cdot \sqrt {21}$$ I assumed this would breakdown to: $$\sqrt{\frac{6}{7}\cdot\frac{21}{1}}$$ The exercise says I should break it down to: $$\sqrt 6\cdot\sqrt\frac{21}{7}$$ What they didn't do is offer…
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Radical under Radical expression

how to find the sum of $\sqrt{\frac54 + \sqrt{\frac32}} + \sqrt{\frac54 - \sqrt{\frac32}} $ ? Is there a method to solve these kind of equations ?
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Why is a fractional exponent a root?

You learn very early that $\sqrt2 = 2^{\frac12}$ and $\sqrt[3]{8} = 8^{\frac13}$ but why is this? Usually when I ask this I get the answer, "Because it is defined that way" but is there any logical reason why fractional exponents are roots?
user169330
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How to Simplify Fractions with Radicals

I am returning to school...algebra...trying to use quadratic formula to solve for $x$, have problem seeing how to simplify fractions with radicals. Is there a step by step guide? I am currently stuck on simplifying the number $\;\sqrt{ \dfrac…