(a − 1/a)^2 − (a + 1/a)^2 =

(A) 4
(B) -4
(C) 2
(D) -2
(E) 2a

(B) -4

Step-by-step explanation:

so, do the multiplications and see :

(a - 1/a)² = a² - 2×a/a + 1/a² = a² - 2 + 1/a²

(a + 1/a)² = a² + 2×a/a + 1/a² = a² + 2 + 1/a²

now we need to subtract the second from the first :

(a² - 2 + 1/a²) - (a² + 2 + 1/a²) =

= a² - 2 + 1/a² - a² - 2 - 1/a² = -4

and that's it !

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: