Sylvester's Inertia Law
The numbers of Eigenvalues that are Positive, Negative, or 0 do not change under a congruencetransformation. Gradshteyn and Ryzhik (1979) state it as follows: when a Quadratic Form 
in 
variables is reducedby a nonsingular linear transformation to the form
the number
of Positive Squares appearing in the reduction is an invariant of theQuadratic Form and does not depend on the method of reduction.See also Eigenvalue, Quadratic Form
References
Gradshteyn, I. S. and Ryzhik, I. M. Tables of Integrals, Series, and Products, 5th ed. San Diego, CA: Academic Press, p. 1105, 1979.
- Lehmer Number
- Lehmer-Schur Method
- Lehmer's Constant
- Lehmer's Formula
- Lehmer's Phenomenon
- Lehmer's Problem
- Lehmer's Theorem
- Lehmus' Theorem
- Leibniz Criterion
- Leibniz Harmonic Triangle
- Leibniz Identity
- Leibniz Integral Rule
- Leibniz Series
- Lemarié's Wavelet
- Lemma
- Lemniscate
- Lemniscate Case
- Lemniscate Constant
- Lemniscate Function
- Lemniscate Inverse Curve
- Lemniscate (Mandelbrot Set)
- Lemniscate of Bernoulli
- Lemniscate of Gerono
- Lemoine Axis
- Lemoine Circle