1.1.28. d - c(b/a) not equal 0, or ad-bc not equal 0.

1.4.14. No. The equation Ax=u has no solution.

1.4.18. Only 3 rows contains a pivot position. The equation Bx=y does not
have a solution for each y in R^4, by Thm 4.

1.4.24. TTTTFT.

1.5.10. x = x_2 (-3,1,0,0,) + x_3 (0,0,1,0) + x_4 (4,0,0,1)

1.5.30. a yes, b no.

1.5.32. a yes, b yes.

1.6.12. a
	x_1 = 100 + x_3 - x_5
	x_2 = 100 - x_3 + x_5
	x_3 = free
	x_4 = 60 - x_5
	x_5 = free
	b min value of x_1 is 40.

1.7.2. lin indep.

1.7.28. It must have 5 pivot columns.

1.9.2.	[1 4 -5]
	[3 -7 4]

1.9.10.	[0 -1]
	[-1 0]

2.1.8. B has 3 rows.

2.1.10. AB = AC =	[1 -7 ]
			[-2 14]

2.2.6. x_1=2 and x_2=5

2.2.32. Not invertible.

2.3.24. Eqn Lx=0 always has the trivial solution. This fact gives no
information about the cols of L.

2.5.2. Ly=b gives y=(2,-2,2), Ux=y gives x=(1/4,2,1).

3.1.8. -11

3.1.10. -6. Start with row 2.

3.1.12. 36. Start with row 1 or col 4.

3.2.6. -18.

3.2.16. 21.

3.2.22. Not invertible.

3.2.24. Lin indep.