x^3+1/x^3=18 then find X+1/x
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Answer:
Let x+1/x = t
Cubing both sides
x^3 + 1/x^3 + 3(x+1/x) = t^3
Now,
x^3+1/x^3 = 18
but, x+1/x = t
so,
18+3t = t^3
Clearly,
t=3 satisfies this equation.
and hence,
x+1/x = 3
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