Exam 3 Answer Key | Linear Algebra | MATH 203, Exams of Linear Algebra

Material Type: Exam; Professor: Shapiro; Class: Linear Algebra; Subject: Mathematics; University: George Mason University; Term: Spring 2011;

Typology: Exams

2010/2011

Uploaded on 07/20/2011

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NAME(print): K r)
Math 203 Spring 2OLl-Exam 3
Instructor: J. Shapiro
Work carefully and neatly and remember that I cannot grade what I cannot read. You
must show ail relevant work in the appropriate space. You may receive no credit for a correct
answer if there is insufficient supporting work. Notes, books and graphing or programable
calculators are NOT ALLOWED.
[18pt] 1. Fill in the blanks with.4 (lways), S(ometimes), N(euer)so that the following are correct
statements.
(a) If dim V -- n and if S is a linearly independent subset of V with n vectors, then ,9
A spans I/.
(b)
(c)
(d)
If A is a 4 x 7 matrix, then the dimension of Nul A is Sequal to three.
The vector 3u * 2v is A in Span {r, r}.
If A is a non-invertible matrix, then the columns of ,4 are 5, N linearly inde-
pendent.
(e) If A is invertible, then Nul A A consists of only the zero vector.
(f) If dim V:6 and if .9 is asubset of V with 7 vectors, then ^9 t spans 7.
(f 'r \
[Spts] 2. Let H: 1l I | , ra > 01.
LLgI )
Show that 11 is not a subspace of R2
Lrt u= ( t\
\al
TLr^^ ba*h t^
fS*t u+U:
!A o+ L t'l
l-?
v: ( o
tl .
Oa^d V olt
(i) i/'| c te^r [1
pf3

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NAME(print): K r)

Math 203 Spring 2OLl-Exam 3

Instructor: J. Shapiro

Work carefully and neatly and remember that I (^) cannot grade (^) what I cannot read. You

must show ail relevant work in the appropriate space. You may receive no credit for a correct

answer if there is insufficient supporting work. Notes, books and graphing or programable

calculators are NOT ALLOWED.

[18pt] 1.^ Fill^ in^ the blanks^ with.4^ (lways),^ S(ometimes),^ N(euer)so^ that^ the following^ are correct

statements.

(a) If dim V -- n and if S is a linearly independent subset of V with n vectors, then ,

A spans^ I/.

(b)

(c)

(d)

If A is a 4 x 7 matrix, then the (^) dimension of Nul A is S^ equal (^) to three.

The vector 3u * 2v is A (^) in Span (^) {r, r}.

If A is a non-invertible matrix, (^) then the (^) columns of ,4 are 5, (^) N (^) linearly inde- pendent.

(e) (^) If A is invertible, then Nul A A^ consists of only the zero vector.

(f) (^) If dim V:6 and if .9 is asubset of (^) V with (^) 7 vectors, (^) then (^) ^9 t (^) spans 7.

(f 'r^ \

[Spts] 2.^ Let^ H:^ 1l I | ,^ ra^ >^ 01.

LLgI )

Show that 11 is not a subspace of R

Lrt u= ( t
\al

TLr^^ ba*h^

t^

fS*t u+U:

!A o+^ L^

t'l

l-? v: ( o

tl. Oa^d V^ olt

(i) i/'|^ c^ te^r

[

Vr v-^ v3^ v( v{

f m11oo22^ 5bI^ [r2o 2/b^ rl 3 A:l'Li (^) "^i ?3 '?^ '33^ | -o': (^) | 3 3 I

-'l' (^3) | 111 22s4^ _1^ uoJ^ Looo oo.l

[gpt] (a)^ What^ is^ the^ dimension^ of: (i)^ nul^ A^3 ; (ii)^ cot A 2;^ (iii)

are row equivalent.

row A ?.r

[12pt] (b)^ Give a^ basis^ for^ each^ of^ (i)^ nul^ A; (ii)^ col A;

i\ (^) X,= -lXr'2/rXr-v

X3='lroXq-)xi

/-:\ (^) l-?/s\ f-t^
It \r o \1o I { o^ I I ,/,o^ , | -r^ I \zl,\ (^) J /, (^) \il

[5pt] (c)^ Write^ the^ fourth^ column of^ A^ as a^ linear combination of the^ first^ three^ columns, or

explain why that cannot be done. (Hint: This is quick.)

L ot'h^ o'{^ B

cnQs B^ I^ urQ^

t +Jatr

[16pt] 4.^ Let^ /:^ {.r,a2} and^ B:^ {br,b2} be^ bases^ for^ a^ vector^ space^ V^ and^ suppose^ that ar :^ 2br + 2b2, and a2 :^ br (^) * 2bz.

(iii) row A.

ri) r,i: \

(ir\

ytl/' (^) l.'"'/

Ldd)

(r 1o tlt^ l)

(o o |^ -'/to f^ )