7.20 Differential geometry

Problem: For a two-sheeted hyperboloid, find: 1) the first and second quadratic forms, 2) the principal curvatures. \[ \frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}-\frac{z^{2}}{c^{2}}-1=0 \text {. } \]