It’s very easy to see whether your subtraction is correct. Simply add the difference and the subtrahend. It should equal the minuend. For example, to check the preceding subtraction problem (208 – 135 = 73), add as follows: 73 + 135 = 208. Since the answer here equals the minuend of the subtraction problem, you know your answer is correct. If the numbers are not equal, something is wrong. You must then check your subtraction to find the mistake.

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation:

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step-by-step explanation: