Question

Which of the following are true( with method)
If x - 1/x = 4 then

(A) x^2 + 1/x^2 = 18

(B) x+ 1/x = ±2√5

(C) x^2 - 1/x^2 = ±8√5

(D) x^4 + 1/x^4 = 322

.....Actually all are true but I need *method* to prove (B) & (C)

Answer 1

Answer:

x2+1/x2=18

(x2+1/x2)2=x4+1/x4+2.x4.1/x4

(18)2 = x4+1/x4+2

324-2=x4+1/x4

x4+1/x4=322 ans.

I HOPE IT WILL BE HELP YOU!!!