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racine nieme - UPMC

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€<br />

€<br />

€<br />

€<br />

€<br />

€<br />

€<br />

⎛<br />

Alors ⎜ a<br />

⎝<br />

€<br />

1<br />

n<br />

⎞<br />

⎟<br />

⎠<br />

On montre que €<br />

n<br />

0<br />

€<br />

n<br />

1<br />

n = 0 = 0<br />

1<br />

n<br />

n<br />

1 =1=1<br />

n<br />

n<br />

a n<br />

ab<br />

= a. Ainsi<br />

1<br />

n a est égal à<br />

1<br />

n a vérifie l’équation<br />

2. Propriétés € des <strong>racine</strong>s € nième n<br />

= ( a)<br />

n<br />

= a = a n ( ) 1 ⎛<br />

n = ⎜ a<br />

⎝<br />

n<br />

= a<br />

a<br />

n =<br />

b<br />

a<br />

n<br />

n<br />

b<br />

n<br />

× b<br />

et aussi (avec<br />

n<br />

m<br />

€<br />

nm m n<br />

a = a = a<br />

€<br />

(exple :<br />

3<br />

1<br />

n<br />

n<br />

⎞<br />

⎟<br />

⎠<br />

= ( ab)<br />

1 1<br />

n n = a × b<br />

m ≥ 2) :<br />

⎛ a<br />

⎜<br />

⎝ b<br />

⎞<br />

⎟<br />

⎠<br />

3<br />

64 = € 64<br />

3.<br />

1<br />

−<br />

a<br />

1 n = n<br />

a<br />

1<br />

n<br />

x n = a.<br />

a et € on a a n ( ) 1<br />

n n n<br />

= a<br />

n<br />

= a<br />

1<br />

n<br />

b<br />

6<br />

= 64<br />

Exercice<br />

€<br />

: écrire l’expression<br />

€<br />

= 1<br />

a<br />

1<br />

n<br />

1<br />

n<br />

⎛ 1 ⎞<br />

m ⎜ a ⎟<br />

⎝ ⎠<br />

1<br />

n<br />

1<br />

n<br />

= 2)<br />

5 3 ( ) 1<br />

1 ⎛<br />

mn = a = ⎜ a<br />

⎝<br />

( ) −1<br />

3 3<br />

× 125<br />

1<br />

n<br />

⎞<br />

⎟<br />

⎠<br />

1<br />

m<br />

= a<br />

sous la forme d’une seule puissance.

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