Math 207 Section 5 Spring 2022
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Math 207
Section 5
Spring 2022
TOPICS AND SAMPLE PROBLEMS:
· Topic 1: Linear systems of equations. You should be able to:
1. Find the solution set of a system of linear equations by using the row reduction algorithm.
2. Write such a solution set in parametric vector form, i.e. as p + x1 v1 + . . . + xr vr for vectors p, v1 , . . . , vr and free parameters x1 , . . . , xr .
3. Notice that p = 0 is a solution if the system is homogeneous.
Sample problem: Find the solution set of the equation Ax = b, and give your answer in parametric
form: ┌ 1 2 1) A = '(') 0 0 1 1 2) A = ┌ 2(1) 4(2) |
1 1 0
1 1 |
0 ┐ 1 '(') , ' _ 1(1) ┐ , |
┌ 1 ┐ b = '(') 0 '(') ' ' b = ┌ 0(0) ┐ |
· Topic 2: Row Echelon Form (REF) and Reduced Row Echelon Form (RREF). You should be able
to:
1. Recognize whether a matrix is in REF, RREF, or neither.
2. Find REF and/or RREF of a matrix.
3. Given REF of an augmented matrix [A l b], find the number of solutions to Ax = b.
4. Given REF of a matrix A, determine:
(a) whether, for every choice of b, the equation Ax = b has |A /↓|§A one solution. (b) whether, for every choice of b, the equation Ax = b has |A 诂扌§A one solution.
(c) whether the homogeneous equation Ax = 0 has any nontrivial solutions.
Sample problem: Consider the matrices B := ┐ , C := ┌''' |
2 2 0 |
1 ┐ 1 '(') , ' |
┌ 1 D := '(') 0 ' |
0 1 0 |
2 2 _3 |
1 ┐ 1 '(') _3 |
1) Determine which of the matrices are in REF, which are in RREF, and which are in neither.
2) For each matrix in REF, suppose A is a row equivalent matrix, and determine:
a) whether, for every choice of b, the equation Ax = b has |A /↓|§A one solution
b) whether, for every choice of b, the equation Ax = b has |A 诂扌§A one solution.
· Topic 3: Linear independence and linear dependence. You should be able to:
1. Understand the definition of linear independence and linear dependence.
2. Determine whether vectors are linearly independent or linearly dependent.
Sample problem: For what value(s) of the parameter h are {v1 , v2 , v3 } linearly independent?
┌ 1 ┐ v1 := '(') 1 '(') ,
' '
┌ 1 ┐
v2 := '(') 1 '(') ,
' '
┌ h ┐
v3 := '(') 3 '(')
0
· Topic 4: Span. You should be able to:
1. Determine whether a given vector lies in the span of some other given vectors.
2. Determine whether some given vectors span all of Rm .
3. Give a geometric description for the span of some given vectors.
Sample problem: For what value(s) of the parameter h is c in the span of a and b?
┌ 1 ┐ a := '(') 0 '(') ,
' '
┌ _3 ┐
b := '(') 1 '(') ,
' '
┌ h ┐
c := '(') _5 '(')
_3
· Topic 5: Linear transformations. You should be able to:
1. Find the standard matrix of a linear transformation.
2. Describe the range of the linear transformation as the span of some vectors.
3. Determine whether a linear transformation is one-to-one.
4. Determine whether a linear transformation is onto.
┌ 1 ┐ Sample problem: Let T : R3 → R3 be a linear transformation that maps the vector '(') 0 '(') to
' '
┌ 1 ┐ ┌ 0 ┐ ┌ 1 ┐ ┌ 0 ┐ ┌ 1 ┐
'(') 0 '('), the vector '(') 0 '(') to '(') 0 '('), and the vector '(') 1 '(') to '(') 1 '(')
1 1 1 0 0
1) Find the standard matrix associated with T.
2) Describe the range of T and the set of all x for which T (x) = 0.
3) Is T onto? Justify your answer.
4) Is T one-to-one? Justify your answer.
· Topic 6: Matrix arithmetic. You should be able to compute sums, linear combinations, and products
of matrices whenever they are defined.
Sample problem: Consider the matrices
A := ┌ 8(0) |
1 8 |
3(8) ┐ , |
┌ 1 B := '(') 2 ' |
Calculate each of the following, or explain why
1) CA
2) CA + 2A
3) AB
4) A + C
_ ┐''' , C := ┌3(1)
it is not defined:
3(1) ┐ .
2022-02-18