Subject: matrices

Right now, we are dealing with matrices and we are supposed to solve the following problem on our graphing-calculators:

2a+3b-4c+d=20
 a-2b+3c-5d=-14
3a+4b-2c+3d=19
5a-b+6c+4d=-5

I am a student.

Hi,

I think that what you are expected to do is to write the system of equations as a matrix equation. Let

Then your system of equations can be written

A X = B

To solve this matrix equation you can multiply both sides, on the left, by A-1. That is

A-1 A X = A-1 B

But A-1 A is the 4-by-4 identity matrix I and I X = X so

X = A-1B

Using your calculator, construct A and B, compute A-1 and multiply to get A-1B.

Cheers,
Penny
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