Homework Help: algebra

Posted by Vee on Friday, February 1, 2013 at 7:26am.

PLEASE help with the below.

Solve the system of equations by first expressing it in matrix form as and then evaluating.

a). 3x-2y=5
4x-y =-10

b). 3x -2y =-2
4x -y = 3

algebra - Reiny, Friday, February 1, 2013 at 8:55am
uggghhh, matrices for such simple systems ???

anyway ....

1st one:

3 -2 5
4 -1 -10

1 1 -15 ---> #2 - #1
3 -2 5 ----> #1

1 1 -15 ---> #1
0 5 -50 ---> 3x#1 - #2

1 1 -15 ---->#1
0 1 -10 ---> #2 ÷ 5

1 0 -5 ---#1 - #2
0 1 -10 ---> #2

so x = -5 and y = -10
---------------------------

same thing using substitution

form #2, y = 4x+10
sub into #1
3x - 2(4x+10) = 5
3x - 8x - 20 = 5
-5x = 25
x = -5 , then y = -20+10 = -10

You try the second one, remember in the matrix method there is no one correct way,
what I did above just seemed like a way to me, you might have taken a different path.
algebra - Vee, Friday, February 1, 2013 at 9:56am
Thank you.

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