how did the textbook condense this equation?
given:
x1 + 2x3 + 4x4 = -8
x2 - 3x3 - x4 = 6
3x1 + 4x2 - 6x3 + 8x4 = 0
-x2 + 3x3 + 4x4 = -12

they condensed it to
x1 + 3x3 = 0
x2 - 3x3 = 4
x4 = -2
and stated that x3 is arbitrary

Question

how did the textbook condense this equation?
given:
x1 + 2x3 + 4x4 = -8
x2 - 3x3 - x4 = 6
3x1 + 4x2 - 6x3 + 8x4 = 0
-x2 + 3x3 + 4x4 = -12

they condensed it to
x1 + 3x3 = 0
x2 - 3x3 = 4
x4 = -2
and stated that x3 is arbitrary

anonymous · Answer

Adding 2nd and 4th eqns giv
3x4=-6
x4=-2
Applying the value of x4 in the 1st eqn giv
x1 + 2x3=0
Applying the value of x4 in the 2nd eqn giv
x2 - 3x3 = 4

anonymous · Answer

oooan add together equations like tht? thanks