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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Removing a radical from an addend in an equation?

Given this simple equation: $$ a + b\sqrt{5} = 7\sqrt{5} - 7 $$ I can really easily say that $a = -7$ and $b = 7$, because: $ a + b\sqrt{5} = 7\sqrt{5} - 7 \\ b\sqrt{5} + a = 7\sqrt{5} - 7 \Rightarrow b = 7 \land a = -7 $ But, what if I want to show…
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is (sqrt(3-x)-sqrt(x)) equal to (sqrt(3-2x))?

And viceversa It should be tha same, because sqrt(x)+sqrt(x) = sqrt(2x) If not, why?
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What does the root of a number really mean?

Now we know that: A number raised to n : xⁿ = x * x * x * x ...n A number raised to -n : x⁻ⁿ = 1/x * x * x * x ...n But what would a root of a number (i.e. x¹/ⁿ) be? What would "a number raised to 1/n" be? Or a better way to interpret the question…
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Can I sum summands within square root?

For example, here's an expression: $\sqrt{x^2 + x^2}$. Will it be equal to $\sqrt{2x^2}$?
JustLearn
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How do I calculate easily radical of $124$?

Today I want to do some math exercises and suddenly I found that it asks me how much is radical of 124. However, I have made some researches and it gave me a very long number which is 11, and with huge numbers which is totally wrong. How can I…
Alex A
  • 107
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$\frac{\sqrt{26} - \sqrt{13} - \sqrt{2}+1}{\sqrt{13} -1 }= ? $

$$\frac{\sqrt{26} - \sqrt{13} - \sqrt{2}+1}{\sqrt{13} -1 }= ? $$ My attempt: $$\frac {\sqrt{2}. \sqrt{13} - \sqrt{13}-2 +1}{2} \tag 1$$ Which equals to $$\frac {\sqrt{2}-1}{\sqrt{13} +1} \tag 2 = ...$$ Waiting for your helps.
Liam
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Finding minimum value of $\sqrt{x^2+y^2}$

Find the minimum value of $\sqrt{x^2+y^2}$, given $15x+8y=120$. My attempt: From $15x+8y=120$, I get $y=\frac{120-15x}{8}$. I substitute this value into $\sqrt{x^2+y^2}$, getting $\sqrt{\frac{289x^2-3600x+14400}{64}}$. I am stuck here as…
QuIcKmAtHs
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Simplifying Radical expressions

Simplify $\dfrac{1}{\sqrt 1+\sqrt{2}}+\dfrac{1}{\sqrt{2}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{4}}+\cdots +\dfrac{1}{\sqrt{8}+\sqrt{9}}$
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How do you add/subtract square roots and a non-root?

I'm new to square root addition/subtraction because I haven't done it in a long time, so how do you add or subtract a square root and a non-root? For example, whats 2 + sqrt2? Is the process different if I did 2 + 2sqrt2? *Edit: radical form, if…
米凯乐
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Rational expression multiplied by a radical rational expression: (4 ÷ 9) × √(27 ÷ 8)

Not sure where I need to go to complete: $$\frac 49 \times \sqrt{\frac{27}8}.$$ I can get to $(2/3)^{5/2}$ but also not sure if this is correct.
Justin
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If $x = 5- \sqrt{21}$, find the value of $\dfrac {\sqrt x}{\sqrt{32-2x} - \sqrt{21}}$.

PROBLEM: If $x = 5- \sqrt{21}$, find the value of $\dfrac {\sqrt x}{\sqrt{32-2x} - \sqrt{21}}$. Solution: $$x = 5- \sqrt{21}$$ $$\sqrt x = \sqrt {5- \sqrt{21}}$$ I am unable to continue from here. Any assistance is appreciated.
rst
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Why is there root of -1?

Always have we heard that there isn't a root of a negative number. That's why we call the root of -1 an imaginary number. But why, why do we need it and how even did they discover this case? I would want a good answer, not someone that says "we need…
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Simple division and some radicals

I'm having a lot of trouble figuring out how to evaluate this problem: $$\dfrac{7}{\frac{7\sqrt{85}}{85}}$$ Everything I've found says that the answer is just $1\sqrt{85}$, but I have no idea how to get there. The best thing I can figure out how to…
Conor
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Is it possible to turn $\sqrt\frac12$ into $\sqrt2$? $ \frac{3}{4}\sqrt{\frac{1}{2} } = \frac{3}{8}\sqrt{{2} }$: What is between the left/right sides?

The textbook has the following line: $$ \frac{3}{4}\sqrt{\frac{1}{2} } = \frac{3}{8}\sqrt{{2} } $$ I don't get what is in-between the left and right sides of the equation.
Ramzes
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Is it $100$% true that $\forall n\in \mathbb{R}, \ n^2 = (-n)^2$?

$$Lemma\text{:}\qquad \forall n\in \mathbb{R}, \ n^2 = (-n)^2 \ \because 1 = (-1)^2$$ $$\text{e.g.}\qquad \forall (x, y)\in \mathbb{R}, \ (x - y)^2 = \big(-(y - x)\big)^2 : (x - y)\in \mathbb{R}\ \land \ (x - y) = -(y - x)$$. $$\begin{align}…
Mr Pie
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