Numerical analysis and approximate methods

Two quadratic equations in two variables can in general be solved only by numerical methods (see Numerical Analysis and Approximate Methods ). If one equation is of the first degree, the other of the second degree, a solution may be obtained by solving the first for one unknown. This result is substituted in the second equation and the resulting quadratic equation solved. 

If /I > 4, there is no formula which gives the roots of the general equation. For fourth and higher order (even third order), the roots can be found numerically (see Numerical Analysis and Approximate Methods ). However, there are some general theorems that may prove useful. 

Numerical methods are often used to find the roots of polynomials. A detailed discussion of these techniques is given under Numerical Analysis and Approximate Methods. ... 

See also Numerical Analysis and Approximate Methods and General References References for General and Specific Topics—Advanced Engineering Mathematics for additional references on topics in ordinary and partial differential equations. 

Adjugate Matrix of a Matrix Let Ay denote the cofactor of the element Oy in the determinant of the matrix A. The matrix B where B = (Ay) is called the adjugate matrix of A written adj A = B. The elements by are calculated by taking the matrix A, deleting the ith row and Jth. column, and calculating the determinant of the remaining matrix times (—1) Then A" = adj A/lAl. This definition may be used to calculate A"h However, it is very laborious and the inversion is usually accomplished by numerical techniques shown under Numerical Analysis and Approximate Methods. ... 

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