Equazione di grado superiore al secondo
\(\displaystyle \left( x^2 - 1 \right)^2 = \left( x + 1 \right)^2 \)
\(\displaystyle \sqrt{ \left( x^2 - 1 \right)^2 } = \sqrt{ \left( x + 1 \right)^2 } \)
\(\displaystyle \left( x^2 - 1 \right) = \left( x + 1 \right) \)
\(\displaystyle \left( x - 1 \right) \left( x + 1 \right) = \left( x + 1 \right) \)
\(\displaystyle \left( x - 1 \right) = 1 \)
\(\displaystyle x = 2 \)