Solve the Nested Root Equation: Fifth Root of Square Root of x^10 = √√81

Nested Radical Simplification with Exponent Rules

Solve the following exercise:

x105=81 \sqrt[5]{\sqrt[]{x^{10}}}=\sqrt{\sqrt{81}}

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:09 Let's solve this problem, step by step.
00:12 A regular root, like a square root, is order 2. So, we break down 81 as 9 squared.
00:19 Remember, we multiply the orders of the roots together.
00:23 Now, use that new order as the root for our number.
00:27 Let's apply this idea to our problem.
00:32 See how the root cancels out the square nicely?
00:38 If we have a root of order C, on A to the power B, here's what we do.
00:44 The result is A to the power of B divided by C.
00:48 Let's try that with our problem again.
00:53 Break down 9 as 3 squared.
00:56 And once more, the root cancels the square.
01:00 And that's how we find our solution!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following exercise:

x105=81 \sqrt[5]{\sqrt[]{x^{10}}}=\sqrt{\sqrt{81}}

2

Step-by-step solution

To solve this problem, we'll begin by simplifying both sides of the equation:

  • Simplifying the left-hand side:

x105 \sqrt[5]{\sqrt{x^{10}}} can be rewritten using properties of exponents and roots. The inner square root is (x10)1/2=x1012=x5 (x^{10})^{1/2} = x^{10 \cdot \frac{1}{2}} = x^{5} .

Then, take the fifth root: (x5)15=x515=x1=x (x^{5})^{\frac{1}{5}} = x^{5 \cdot \frac{1}{5}} = x^{1} = x .
Thus, the left-hand side simplifies to x x .

  • Simplifying the right-hand side:

81 \sqrt{\sqrt{81}} simplifies as follows: First, find 81=9\sqrt{81} = 9.
Then, compute 9=3\sqrt{9} = 3.

So, the equation reduces to x=3 x = 3 .

Therefore, the solution to the problem is x=3 \boxed{x = 3} .

3

Final Answer

x=3 x=3

Key Points to Remember

Essential concepts to master this topic
  • Exponent Rule: Convert nested radicals to fractional exponents for easier manipulation
  • Technique: x105=(x10)1215=x1=x \sqrt[5]{\sqrt{x^{10}}} = (x^{10})^{\frac{1}{2} \cdot \frac{1}{5}} = x^1 = x
  • Check: Substitute x = 3: 3105=590495=2435=3 \sqrt[5]{\sqrt{3^{10}}} = \sqrt[5]{\sqrt{59049}} = \sqrt[5]{243} = 3

Common Mistakes

Avoid these frequent errors
  • Working from outside to inside with nested radicals
    Don't start with the fifth root first = x105(5)x10 \sqrt[5]{\sqrt{x^{10}}} ≠ (\sqrt[5]{\sqrt{}})x^{10} ! This breaks the order of operations and creates impossible expressions. Always work from the innermost radical outward: first simplify x10=x5 \sqrt{x^{10}} = x^5 , then take the fifth root.

Practice Quiz

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Choose the largest value

FAQ

Everything you need to know about this question

Why can I write x10=x5 \sqrt{x^{10}} = x^5 directly?

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Since we're dealing with even exponents under square roots, we assume x ≥ 0 for real solutions. When x is positive, x10=x5=x5 \sqrt{x^{10}} = |x^5| = x^5 because x5 x^5 is positive.

How do I simplify 81 \sqrt{\sqrt{81}} step by step?

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Work from the inside out: First find 81=9 \sqrt{81} = 9 , then 9=3 \sqrt{9} = 3 . You can also use exponents: 81=811212=8114=3 \sqrt{\sqrt{81}} = 81^{\frac{1}{2} \cdot \frac{1}{2}} = 81^{\frac{1}{4}} = 3

Can I use the rule amn=anm \sqrt[n]{\sqrt[m]{a}} = \sqrt[nm]{a} ?

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Yes! This is a powerful shortcut: x105=x1052=x1010=x \sqrt[5]{\sqrt{x^{10}}} = \sqrt[5 \cdot 2]{x^{10}} = \sqrt[10]{x^{10}} = x . Both methods give the same answer!

What if x could be negative?

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For real number solutions, we typically assume x ≥ 0 when dealing with even roots. If x were negative, x10 x^{10} would be positive, but x5 x^5 would be negative, complicating the radical simplification.

How do I verify my answer x = 3?

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Substitute back into both sides: Left side: 3105=590495=2435=3 \sqrt[5]{\sqrt{3^{10}}} = \sqrt[5]{\sqrt{59049}} = \sqrt[5]{243} = 3 . Right side: 81=9=3 \sqrt{\sqrt{81}} = \sqrt{9} = 3 . Both equal 3! ✓

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