ordered triple system of equations stumped?
A) 3x+2y+z = -21
B) 2x-5y-z =7
C) 4x+y+5z= -43
The correct answer via TI-84+ is {-4, -2, -5}
But I am determined to figure this out by hand but so far the closest answer I have is
{4 1/13, 2 1/2, 12 3/4}
Steps I took:
1.) Added A and B
A) 3x +2y +z = -21
B) 2x -5y -z = 7
to get:
5x -3y = -14
2) Multiplied B by 5 then Added B and C
[B) 5(2x-5y-z =7)]
C) 4x +y +5z = -43
B) 10x -25y -5z = 35
to get
14x -24y = -8
3) Took step 1's answer and multiplied by -8 and added to step 2's answer
[Step 1) [-8(5x -3y = -14)]
Step 2) 14x -24y = -8
Step 1) -40x +24y = 114
to get
-26x=106
x=-106/26 or 4 1/13 (previous thought it was 3 5/7 so y and z by my calcs are wrong (2 1/2, 12 3/4)
Obviously, I am messing up somewhere... I'd appreciate the help, thanks