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The absolute value of a number is always non-negative, so when n is even, the result will always be non-negative. Consider a few example nth roots that can be simplified by using the formula.
a | n | nan | Is n even? | Simplify |
---|---|---|---|---|
4 | 3 | 343 | × | 4 |
-6 | 5 | 5(-6)5 | × | -6 |
2 | 6 | 626 | ✓ | ∣2∣=2 |
-3 | 4 | 4(-3)4 | ✓ | ∣-3∣=3 |
To write the expression for nan, there are two cases to consider.
Both cases will be considered one at a time.
In case of a negative value of a, there are also two cases two consider.
(-a)ne=ane
na=an1
(am)n=am⋅n
a⋅a1=1
a1=a
If a is non-negative, nan is always equal to a. However, in case of negative a, the value of nan depends on the parity of n.
a≥0 | a<0 | |
---|---|---|
Even n | nan=a | nan=-a |
Odd n | nan=a | nan=a |
To conclude, for odd values of n, the expression nan is equal to a. On the other hand, if n is even, nan can be written as ∣a∣.
Depending on the index of the root and the power in the radicand, simplifying nam may be problematic. Because real nth roots with an even index are defined only for non-negative numbers, the absolute value is sometimes needed.
If n is even, nam is defined only for non-negative am.
a | m | n | nam | Simplify |
---|---|---|---|---|
2 | 8 | 4 | 428 | 248=22=4 |
-3 | 6 | 2 | (-3)6 | ∣∣∣∣(-3)26∣∣∣∣=∣∣∣(-3)3∣∣∣=∣-27∣=27 |
x | 6 | 3 | 3x6 | x36=x2 |
-3 | 2 | 8 | 8(-3)2 | 4∣-3∣=43 |
2 | 3 | 6 | 623 | 2 |
-2 | 3 | 9 | 9(-2)3 | 3-2 |
2 | 6 | 8 | 826 | 423=48 |
-2 | 6 | 8 | 8(-2)6 | 4∣-2∣3=423=48 |