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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comparing small sums of radicals

Let $a,b,c,d,e$ be positive integers, and suppose it is simple to compare integers to each other, but difficult to compare irrationals, and we want to compare sums of square roots. As a simple example, we can show that $\sqrt{a}+\sqrt{b}>\sqrt{c}$…
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Square root of square as 2/2 power

From school I know that $\sqrt{x^2} = |x|$. But if we rewrite the above equation in another way $\sqrt{x^2} = (x^2)^{\frac{1}{2}} = x^{\frac{2}{2}} = x^1 = x$ then we get another answer. How is it possible that rewritting an equation changes the…
user646847
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Distance Formula with Negative Weights

I currently have a series of points in $n$-dimensional space and a series of weights. I wish to calculate the weighted distance between two points, using the following formula: $$d(a,b) = \sqrt{\sum_{i=0}^n w_i \left(X_i(a) -…
lioness99a
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$\sqrt[5]{2^4\sqrt[3]{16}} = ? $

$$\sqrt[5]{2^4\sqrt[3]{16}} = ? $$ Rewriting this and we have $$\sqrt[5\cdot 3]{2^{4\cdot 3}4}$$ $$\sqrt[15]{2^{12}2^2}$$ Finally we get $$\sqrt[15]{2^{12}2^2} = \sqrt[15]{2^{14}} = 2^{\frac{15}{14}}$$ Am I right?
Fiv
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$\sqrt{3-\sqrt5}+\sqrt{3+\sqrt5}$

$$\sqrt{3-\sqrt5}+\sqrt{3+\sqrt5}$$ I'm trying to get the term $$\sqrt{x\pm2\sqrt y}$$ However, I don't know how to.
Goendo
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Why is $\sqrt x \times \sqrt y = \sqrt {xy}$

Sorry I do not know latex. Why is $\sqrt x \times \sqrt y = \sqrt {xy}$? It also applies for division, but why not addition and subtraction? i.e., why is $\sqrt x + \sqrt y$ not equal to $\sqrt {x+y}$? Thank you for editing and answering.
Ram Keswani
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Formula for square root inside a square root

I am trying to remember a formula from high school about nested square roots. It goes something like this: $\sqrt{\frac{a+\sqrt{b}}{c}} = \sqrt{\frac{?}{?}} \pm \sqrt{\frac{?}{?}} $ This formula is supposed to eliminate nested squares, so there are…
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Solving Radicals in One Variable

I recently encountered a question from my math textbook (I write as a Grade 12 math student) which presented a radical equation to be solved. I did so, but in a messy way. Writing this question serves me the purpose of having it simplified. The…
N.N.
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Why $\sqrt{x^2}$ is not equal to $\big(\sqrt{x}\big)^2$?

I'm reading Precalculus from James Stewart. In the book, the author says that $\sqrt{x^2}$ is not equal to $\big(\sqrt{x}\big)^2$. I was performing a couple of proofs and I ended up here: If you have, for example: $\sqrt{5^2} ≟ \big(\sqrt{5}\big)^2…
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What theorem or corollary allows one to take the limit of an expression raised to a positive rational number $\lt$ 1?

I was presented with theorems which state: If $\lim_{x\to a}f(x) = l$ and $\lim_{x\to a}g(x) = m$, then $$\lim_{x\to a}(f \cdot g)(x) = l \cdot m$$ $$\lim_{x\to a}(f + g)(x) = l + m$$ if $m \neq 0$,$$\lim_{x\to a}\Bigl(\frac 1g\Bigr)(x) = \frac 1m$$…
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What is the mathematical mystery here?

I know that, $$\sqrt{25}=5≠-5$$ But, in quadratic equation we write $$(2ax+b)^2=b^2-4ac$$ $$(2ax+b)=±\sqrt{b^2-4ac}$$ Why?? We must write $±$, and What is the mathematical mystery here?
Soru
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Solving radical equations

How to solve the following equation without graphing it? I have tried graphing it and got the answer y=121. It appears as a linear function, but I do not know why it gives a line. The equations is as follows: $$y+\sqrt{y}-132=0$$ How may I solve it…
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Can a negative radical be expressed in terms of positive radical?

I want to get rid of negative radicals, but I guess this is not possible. Assume I have: $$-\sqrt{c}$$ Where $c$ is from $\mathbb Q^+$. Can I express this as follows, where a and b are from $\mathbb Q^+$: $$-a + \sqrt{b}$$
user4414
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simple squaring of a radical

I am a little confused with the following calculation of a radical. $$\left(-\frac {\sqrt{-r}}{2} \right)^2=-\frac{r}{4}$$ $$\left(\frac {\sqrt{-r}}{2} \right)^2=-\frac{r}{4}$$ I would have thought both of these solutions would be, $$\frac…
fr14
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Subtracting two square roots

How should one subtract the following square roots? I am aware of the fact that you can only add or subtract two square roots if their 'radical part' is the same. $\displaystyle y^* = \sqrt{\frac{2KD}{h}} \cdot \sqrt{\frac{s+h}{s}}$ $\displaystyle…
Anna D.
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