SOLUTION: Find matrix X: AX= B 1. A= [6,5] B= [18,49] [4,-2] [-20,6] 2. A= [3,4] B= [10,-10] [-3,-2] [-8,8]

Algebra ->  Matrices-and-determiminant -> SOLUTION: Find matrix X: AX= B 1. A= [6,5] B= [18,49] [4,-2] [-20,6] 2. A= [3,4] B= [10,-10] [-3,-2] [-8,8]      Log On


   



Question 173807: Find matrix X: AX= B
1. A= [6,5] B= [18,49]
[4,-2] [-20,6]

2. A= [3,4] B= [10,-10]
[-3,-2] [-8,8]

Answer by Mathtut(3670) About Me  (Show Source):
You can put this solution on YOUR website!
 
:
We must find the inverse of matrix A in order to solve for x
:
A= [6,5]
[4,-2]
:
take terms a%5B11%5Dand a%5B22%5D and switch their positions. This is simply switching the elements on the main diagonal

take terms a%5B12%5Dand a%5B21%5D and change those numbers to their opposites keeping there positions.
%28matrix%282%2C2%2C-2%2C-5%2C-4%2C6%29%29-revised matrix
:now we find the determinant of this matrix
:
product of the main diagonal minus the product of the off diagonal
:
-12-20=-32
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we take that result and divide every element in the revised matrix and the result is our inverse matrix
:
%28matrix%282%2C2%2C1%2F16%2C5%2F32%2C1%2F8%2C-3%2F16%29%29
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Now we have to multiply each side of the equation AX=B by the matrix A's inverse
On the left hand side we will end up with the indentity matrix multiplied by X which is equal to just X. So X=A%5E-1%28B%29
:
A= [6,5] B= [18,49]
[4,-2] [-20,6]
:
so
X=%28matrix%282%2C2%2C1%2F16%2C5%2F32%2C1%2F8%2C-3%2F16%29%29*%28matrix%282%2C2%2C18%2C49%2C-20%2C6%29%29---->
:
=%28matrix%282%2C2%2C-2%2C4%2C6%2C5%29%29
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2) I will leave the details and steps of # 2 to you
:
the answer is %28matrix%282%2C2%2C2%2C-2%2C1%2C-1%29%29