(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 !

ok

step-by-step explanation:

14.3

step-by-step explanation:

add all the numbers together.

9 + 12 + 15 + 16 + 17 + 17 = 86

now, divide 86 by how many numbers we have: 6.

86 / 6 = 14.3