SOLUTION: Dear tutor,I 've checked one of the problems which was like my question but I couldn't mach the answer with mine.could you help me in this way ? Choose the answer Of {{{x^4+1/x^4

Algebra ->  Exponents -> SOLUTION: Dear tutor,I 've checked one of the problems which was like my question but I couldn't mach the answer with mine.could you help me in this way ? Choose the answer Of {{{x^4+1/x^4      Log On


   

Question 201628: Dear tutor,I 've checked one of the problems which was like my question but I couldn't mach the answer with mine.could you help me in this way ?
Choose the answer Of x%5E4%2B1%2Fx%5E4 if x%2B1%2Fx=8:
a.)8%5E4
b.)8%5E4%2B2%5E8
c.)8%5E4%2B2%5E8-2
d.)8%5E4%2B2
e.)8%5E4-2%5E8%2B2
Answer by RAY100(1637) About Me  (Show Source):
You can put this solution on YOUR website!
x + 1/x =8
(x^2 +1 ) / x =8
x^2 +1 = 8x
x^2 -8x +1 =0
.
using quadratic eqn,, x= 7.873,,.127
,
substitute either in
.
X^4 +(1/x^4) = 3842
.
checking answers, this matches (E) (8^4 -2^8 +2)