Tarnisa bought 4 sandwiches for her and her three friends. She had a coupon for $2 off each sandwich and spent a total of $18. I
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These array of numbers shown above are called matrices. These are rectangular arrays of number that are arranged in columns and rows. It is mostly useful in solving a system of linear equations. For example, you have these equations
x+3y=5
2x+y=1
x+y=10
In matrix form that would be
![\left[\begin{array}{ccc}1&3&5\\2&1&1\\1&1&10\end{array}\right]](https://tex.z-dn.net/?f=%20%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D1%263%265%5C%5C2%261%261%5C%5C1%261%2610%5Cend%7Barray%7D%5Cright%5D%20)
where the first column are the coefficients of x, the second column the coefficients of y and the third column is the constants, When you multiple matrices, just multiply the same number on the same column number and the same row number. For this problem, the solution is
![\left[\begin{array}{ccc}3*2&0*8\\2*0.6&-1*3\end{array}\right] = \left[\begin{array}{ccc}6&0\\1.2&-3\end{array}\right]](https://tex.z-dn.net/?f=%20%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D3%2A2%260%2A8%5C%5C2%2A0.6%26-1%2A3%5Cend%7Barray%7D%5Cright%5D%20%3D%20%20%5Cleft%5B%5Cbegin%7Barray%7D%7Bccc%7D6%260%5C%5C1.2%26-3%5Cend%7Barray%7D%5Cright%5D%20)
x+3y=5
2x+y=1
x+y=10
In matrix form that would be
where the first column are the coefficients of x, the second column the coefficients of y and the third column is the constants, When you multiple matrices, just multiply the same number on the same column number and the same row number. For this problem, the solution is