Question

Se x + 1/x = 5, quanto vale x² + 1/x²?

Answer 1

$x+\frac{1}{x}=5\\ \\ (x+\frac{1}{x})^2=25\\ \\ x^2+2+\frac{1}{x^2}=25\\ \\ x^2+\frac{1}{x^2}=25-2\\ \\ \boxed{x^2+\frac{1}{x^2}=23}$