Math 43, Fall 2007
B. Dodson
Week 6:
Recall that the graded homework has been
postponed
to Wednesday, after the break. See the
Text Examples
2.27 and 2.28 for the method used on
graded homework 6. Section 2.4 will
NOT
be covered
on Friday’s exam.
Room Change.
Both hour exams will be in Williams 301,
at our usual class time, 11:1012:00.
We’ve spent this week on linear combinations, spanning,
linear independence, linear dependence and explicit relations
of linear dependence; as on suggested homeworks 5 and 6.
These topics are on our exam syllabus.
Problem 2.2, #30 (suggested Hw 5)
Solve the system of equations

x
1
+ 3
x
2

2
x
3
+ 4
x
4
= 0
2
x
1

6
x
2
+
x
3

2
x
4
=

3
x
1

3
x
2
+ 4
x
3

8
x
4
= 2
Solution
We know immediately that this system is either
inconsistent or has inﬁnitely many solutions. (Why?)
(more variables than equations.)
Unless we ﬁnd an inconsistency, we should use GaussJordan
(not Gaussian elimination), and include a reduced row echelon
matrix. (
Note:
this is part of the solution.)
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 Spring '08
 Dodson
 Math, Linear Algebra, Vector Space, Row echelon form

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