I have a question

soccerball3211

Junior Member
Joined
May 16, 2005
Messages
84
I know how to get the answer(-1660) using the calculator but can anyone show me how to get the answer using the row reduction method. I keep getting:
[5 -15 -25 30]
[0 1 -8 1]
[0 9 2 1]
[0 15 24 -23]

What am I doing wrong?
 

Gene

Senior Member
Joined
Oct 8, 2003
Messages
1,904
You don't say what you are getting. That makes it hard to guess what's wrong.
Multiply row 1 by .2
Code:
[1  -3  -5   6] 
[0   1  -8   1] 
[0   9   2   1] 
[0  15  24  -23]
Multiply row 2 by -9 and add to row 3
Code:
[1  -3  -5   6] 
[0   1  -8   1] 
[0   0  74  -8] 
[0  15  24  -23]
Multiply row 2 by -15 and add to row 4
Code:
[1  -3  -5   6] 
[0   1  -8   1] 
[0   0  74  -8] 
[0   0 144  -38]
1*1*(74*(-38) - (-8)*144) = -1660
 

soccerball3211

Junior Member
Joined
May 16, 2005
Messages
84
This is the problem here, and I have to evaluate it.
[1 -3 -5 6]
[0 1 -8 1]
[0 9 2 1]
5 0 -1 7]

I chose to subtract 5 times row 1 from row 4 and it doesn't come out to -1660. I dont know what Im doing wrong.
What I posted before was what I got after I multiplied the first row by 5 and then subtracted it from row 1.

IS there something wrong with my math. HELP
 

soccerball3211

Junior Member
Joined
May 16, 2005
Messages
84
I figured it out thanx for the help
 
Top