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If the discriminant is positive, the number of non-real roots is a multiple of 4. That is, there is a nonnegative integer k ≤ n /4 such that there are 2 k pairs of complex conjugate roots and n − 4 k real roots.
Specifically, if the eigenvalues all have real parts that are negative, then the system is stable near the stationary point. If any eigenvalue has a real part that is positive, then the point is unstable. If the largest real part of the eigenvalues is zero, the Jacobian matrix does not allow for an evaluation of the stability. [12]
In cases 1 and 2, the requirement that f xx f yy − f xy 2 is positive at (x, y) implies that f xx and f yy have the same sign there. Therefore, the second condition, that f xx be greater (or less) than zero, could equivalently be that f yy or tr( H ) = f xx + f yy be greater (or less) than zero at that point.
If the discriminant is negative, then the parabola opens in the opposite direction, never crossing the -axis, and the equation has no real roots; in this case the two complex-valued roots will be complex conjugates whose real part is the value of the axis of symmetry.
The above formula shows that its Lie algebra is the special linear Lie algebra consisting of those matrices having trace zero. Writing a 3 × 3 {\displaystyle 3\times 3} -matrix as A = [ a b c ] {\displaystyle A={\begin{bmatrix}a&b&c\end{bmatrix}}} where a , b , c {\displaystyle a,b,c} are column vectors of length 3, then the gradient over one ...
The discriminant of K is 49 = 7 2. Accordingly, the volume of the fundamental domain is 7 and K is only ramified at 7. In mathematics, the discriminant of an algebraic number field is a numerical invariant that, loosely speaking, measures the size of the (ring of integers of the) algebraic number field.
If the discriminant is zero the fraction converges to the single root of multiplicity two. If the discriminant is positive the equation has two real roots, and the continued fraction converges to the larger (in absolute value) of these. The rate of convergence depends on the absolute value of the ratio between the two roots: the farther that ...
If the three roots are real and distinct, the discriminant is a product of positive reals, that is > If only one root, say r 1 , is real, then r 2 and r 3 are complex conjugates, which implies that r 2 – r 3 is a purely imaginary number , and thus that ( r 2 – r 3 ) 2 is real and negative.