The sum of two numbers is 39. Their difference is 21. What are the two numbers?

30 and 9

Step-by-step explanation:

x+y=39 , x-y=21

Solve for x:

x+y=39 , x-y=21

x= 30

Substitute x with 30:

(30)+y=39 , (30)-y=21

Solve for y:

y=9

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: