SOLUTION: Solve by introducing a substitution that transforms these equations to quadratic form x^(-8)-17x^(-4)+16=0

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Question 339921: Solve by introducing a substitution that transforms these equations to quadratic form
x^(-8)-17x^(-4)+16=0
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let u=x%5E%28-4%29, then u%5E2=x%5E%28-8%29,
u%5E2-17u%2B16=0
%28u-1%29%28u-16%29=0
Two u solutions:
u-1=0
u=1
x%5E%28-4%29=1
x%5E%284%29=1
x%5E4-1=0
%28x%5E2-1%29%28x%5E2%2B1%29=0
%28x-1%29%28x%2B1%29%28x%5E2%2B1%29=0
Four x solutions: x=-1,1,-i,i
.
.
.
u-16=0
u=16
x%5E%28-4%29=16
x%5E%284%29=1%2F16
x%5E4-1%2F16=0
%28x%5E2-1%2F4%29%28x%5E2%2B1%2F4%29=0
%28x-1%2F2%29%28x%2B1%2F2%29%28x%5E2%2B1%2F4%29=0
Four x solutions: x=-1%2F2,1%2F2,-%281%2F2%29i,%281%2F2%29i