Why is it different?

Why is x23 \sqrt[3]{x^2} different from x2/3x^{2/3} ?

#Algebra

Note by Bile Carlos
5 years, 1 month ago

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Comments

For real numbers they are equivalent. In the complex case, i23\sqrt[3]{i^2} usually means the real third root of 1-1, whereas i23i^\frac{2}{3} usually refers to the principalprincipal third root of 1-1 (it has three third roots), which is 12+32i\frac{1}{2} + \frac{\sqrt{3}}{2} i. For instance, you'll get these different values if you enter the expressions in Google or Wolfram Alpha. Enter "cube root of i^2" and you get -1; enter "i^(2/3)" and you get 0.5 + 0.866025404 i. This is purely conventional. (Wolfram helpfully tells you, "Assuming 'cube root' is the real-valued root".)

Mark C - 5 years, 1 month ago

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Yep but, the domain of third root of x^2 is different from the domain of x^(2/3). How is that possible??

Bile Carlos - 5 years, 1 month ago

There is no difference in the above expressions

Sai B - 5 years, 1 month ago

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Yep but, the domain of third root of x^2 is different from the domain of x^(2/3). How is that possible??

Bile Carlos - 5 years, 1 month ago

There is no difference in the two expressions. But since you are asking then:

x23=x23\sqrt[3]{x^2}=x^{\dfrac{2}{3}}

But

x23=(x)2132=(x)223\large \sqrt{x^{\sqrt[3]{2}}}=(x)^{\dfrac{2^{\frac{1}{3}}}{2}}=(x)^{{2^{-\frac{2}{3}}}}

Hope this helps. \smile

Abhay Tiwari - 5 years, 1 month ago

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Yep but, the domain of third root of x^2 is different from the domain of x^(2/3). How is that possible??

Bile Carlos - 5 years, 1 month ago
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