Question

Se x+1/x=5 quanto vale x²+1/x²?

Answer 1

Oi 

(x + 1/x)² = x² + 2x/x + 1/x² = x² + 2 + 1/x² = 5²

x² + 1/x² = 5²  - 2 = 25 - 2 = 23

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