Upper Sum 6 -2 2 4 16 0 -4 2 2 -6 0 0 2 -5 -9 0 0 0 -3 -3 ●Last equation:-3x4=-3→x4=1 .Second to last equation:23-5 4 =23-5=-9 3=-2 =1 ..second equation...2=... ·12x3x4=B1-21]T 7 For small problems,check solution in original system. Copyright©2011，NA⊙Yin Last Modification:Oct.2011 10Upper Sum   6 −2 2 4 16 0 −4 2 2 −6 0 0 2 −5 −9 0 0 0 −3 −3   • Last equation: −3x4 = −3 ⇒ x4 = 1 • Second to last equation: 2x3 − 5 x4 |{z} =1 = 2x3 − 5 = −9 ⇒ x3 = −2 • . . . second equation . . . x2 = . . . • x1 x2 x3 x4 T = 3 1 −2 1T For small problems, check solution in original system. Copyright c 2011, NAYin Last Modification: Oct. 2011 10