Umm Al-Qura University بسم الله الرحمن الرحيم Umm Al-Qura University Health Sciences College at Al-Leith Department of Public Health Lecture (10)

Matrices Multiplication

Objectives: 1/ Define Matrix Multiplication Low. 2/ Explain How do you Multiple tow Matrices. 3/ Give an Example of Matrix Multiplication.

Multiplication of matrices How do I multiply two matrices? Two matrices [A] and [B] can be multiplied only if the number of columns of [A] is equal to the number of rows of [B] to give If [A] is a mxp matrix and [B] is a pxn matrix, the resulting matrix [C] is a mxn matrix.

Example Given find [C] = [A][B] Solution

C11 = [ ] C11 = [(5)(3) + (2 )(5) + (3)(9) ] = [15+10+27] = 52

C21 = C21 = [(1)(3) + (2 )(5) + (7)(9) ] = [3+10+63] = 76

C22 = C22 = [(1)(-2) + (2 )(-8) + (7)(-10) ] = [-2+-16+-70] = -88

Homework If we have the following matrices Find 1) A B 2) 3B + C 3) A C 4) 2B - A

Thanks Radia