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Inverses. Definition. For any two matrices A and B, if AB = BA = I , then A and B are called inverse matrices The symbols A -1 denotes the inverse of matrix A If A = and det A ≠ 0 then A -1 = If det A = 0, then A has no inverse. Example 1. Find A -1 if A =
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Definition • For any two matrices A and B, if AB = BA = I, then A and B are called inverse matrices • The symbols A-1 denotes the inverse of matrix A • If A = and det A ≠ 0 then A-1 = • If det A = 0, then A has no inverse
Example 1 • Find A-1 if A = • First find the determinant • Interchange a and d, replace both b and c with their opposites and then multiply the resulting by 1/det A
Practice • Page 792 WE #1 – 8
How to convert a SOE to a Matrix • Covert the SOE to a matrix
Practice • Page 792 WE #9 – 16
Using matrices to solve SOE • Use matrices to solve this system: • Write the SOE as a matrix equation • Find the determinant of the coefficient matrix • If equal to zero no unique solution • Find the inverse of the coefficient matrix • Multiply the inverse matrix by the coefficient matrix and the solutions matrix • The solution of the equation AX = B is X = A-1B
Practice • Page 792 WE #9 – 16