#4**+10 **

Hi Coldplay,

A matrix is an array of numbers.

It is used a lot to solve difficult simultaneous equations where there is more than 2 unknowns.

If there are 2 unknowns you need 2 equations

If there are 3 unknowns you need 3 equations.

The coefficients of the letters (pronumerals) are the numbers that go into the array.

Have a look at this introduction

Guest Jan 7, 2016

#2**+6 **

-5x - y = 21 → y = -21 - 5x (1)

3x - 4y + 5z = - 8 (3)

-3x - z = 12 → z = -3x -12 (2)

Substituting (1) and (2) into (3), we have

3x - 4(-21 - 5x) + 5(-3x -12) = - 8 simplifiy

3x + 84 + 20x - 15x - 60 = -8

8x + 24 = -8 subtract 24 from both sides

8x = - 32 divide both sides by 8

x = -4

And using (1) y = -21 - 5(-4) = -21 + 20 = -1

And using (2) z = -3(-4) - 12 = 12 - 12 = 0

So (x, y, z) = (-4 , -1 , 0)

CPhill Jan 7, 2016

#3**+4 **

Note, Paypay.......we could have used Gaussian Elimination to solve this....but......I don't know if you have covered that, or not.......also.......it's kind of tedious......!!!!!

I just went the Algebra route........!!!!

CPhill Jan 7, 2016

#4**+10 **

Best Answer

Hi Coldplay,

A matrix is an array of numbers.

It is used a lot to solve difficult simultaneous equations where there is more than 2 unknowns.

If there are 2 unknowns you need 2 equations

If there are 3 unknowns you need 3 equations.

The coefficients of the letters (pronumerals) are the numbers that go into the array.

Have a look at this introduction

Guest Jan 7, 2016