Question

find the system of equations
2x+2y+z=20
2y+5z=10
4y-7z=20

Answer 1

you listen the system of equations

Answer 2

what.?

Answer 3

you listed the system of equations*

Answer 4

find the matrix representation of the system of equations?

Answer 5

ohh my bad it's supposed to say solve the system of equations

Answer 6

ahh

Answer 7

linear algebra or not?

Answer 8

are you learning matrix operations?*

Answer 9

yea

Answer 10

row reduction?

Answer 11

hmm its sort of hard to show how to do this on here, let me learn how to input matrices that are 3*4

Answer 12

2 2 1 20
0 2 5 10
0 4 -7 20

is it ok if I just write the matrix like that/do you see how I came up with that matrix?

Answer 13

ok I guess find me when you have some time......lol

Answer 14

yea

Answer 15

sorry my laptop died

Answer 16

:P

Answer 17

ok
so we want the form

1 0 0 a
0 1 0 b
0 0 1 c

we have

2 2 1 20
0 2 5 10
0 4 -7 20

multiply the second row by -2 and then add the 2nd row to the third row

2 2 1 20
0 2 5 10
0 0 -17 0

tell me when this makes sense

Answer 18

note we essentially added one equation to another, this is ok....

a=b and c=d
then
a+c=b+d

Answer 19

okay I understand go on

Answer 20

now divide everything in the bottom row by -17
2 2 1 20
0 2 5 10
0 0 1 0

Answer 21

multiply the bottom row by -5 and add it to the middle row
2 2 1 20
0 2 0 10
0 0 1 0
divide middle row by 2
2 2 1 20
0 1 0 5
0 0 1 0
multiply the bottom row by -1 and add it to the top row
2 2 0 20
0 1 0 5
0 0 1 0
divide the top row by 2
1 1 0 10
0 1 0 5
0 0 1 0
multiply the middle row by -1 and add to the first
1 0 0 5
0 1 0 5
0 0 1 0

the column vector on the right is the answer
x = 5, y = 5, z = 0

Answer 22

ohhh ...

Answer 23

note the pattern I took, first we get the lower triangle to be 0's then the upper
do lower first