Let A and let x vector Find the solution of the homogeneou
Solution
A = 1 2 -3
2 1 -3
-1 1 0
X = X1
X2
X3
a)
Ax = 0
we multiply matrix A with matrix x and put it equal to zero
1x1 +2x2 -3x3 0
2x1 +1x2 -3x3 = 0
-1x1 +1x2 +0x3 0
we get
1x1 +2x2 -3x3 = 0 (1)
2x1 +1x2 -3x3 = 0 (2)
-1x1 +1x2 = 0 (3)
now we have 3 equations
we can solve for x1,x2 and x3
eq(1) -eq(2) we get
-1x1 +1x2 = 0
we get eq(3) so we cannot solve this
x1 = t
from (3) we have
x2 = t
from (2)
3t -3x3 =0
x3 = t
x1 1
x2 = t ( 1 )
x3 1
b)
A = 1 2 -3
2 1 -3
-1 1 0
X = X1
X2
X3
and
B= 5
13
-8
ax = b
1x1 +2x2 -3x3 = 5 (1)
2x1 +1x2 -3x3 = 13 (2)
-1x1 +1x2 = -8 (3)
we cannot sove these
therefore from (3)
x2= -8+1x1 let x1 = t
x2 = - 8 + t (4)
x2 = t - 8
from (2)
2x1 +1x2 -3x3 = 13
2t + (t - 8) -3x3 = 13
3t - 8 -3x3 =13
-3x3 = 13+8-3t
3x3 = 3t - 21
x3 = t - 7
x1 1 0
x2 = t * ( 1) - 1 (8)
x3 1 7


