Math 205B Exam 01 - Linear Algebra Problems, Exams of Linear Algebra

The first five pages of an exam from a linear algebra course (math 205b) focusing on finding solutions for linear equations, linear transformations, and linear independence. Students are required to find parametric solutions, check conditions for linear independence and span, and perform matrix operations.

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2012/2013

Uploaded on 02/27/2013

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Math 205B Exam 01 page 1 02/12/2010 Name
1. Let A=
2 3 5 1
4 3 7 7
3 2 5 6
, let b=
b1
b2
b3
and let c=
15
3
5
.
1A. Find all solutions of Ax=cand write your answer in parametric vector form x=p+vhwhere pis a particular
solution of Ax=cand and vhrepresents all solutions of the homogeneous equation Ax=0.
1B. Find any/all conditions on b1,b2and b3which are necessary and sufficient for bto be in the span of the set of column
vectors of A.
1C. Give the correct definition: What does it mean to say a set of vectors S={v1,v2, . . . , vp}is linearly independent?
“We say Sis linearly independent if and only if. . . [you complete the definition:]
1D. Do the column vectors of Aform a linearly independent set? Explain in terms of the definition of linear independence.
1E. Do the column vectors of Aspan R3? Explain.
pf3
pf4
pf5

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  1. Let A =

, let b =

b 1 b 2 b 3

 (^) and let c =

1A. Find all solutions of Ax = c and write your answer in parametric vector form x = p + vh where p is a particular solution of Ax = c and and vh represents all solutions of the homogeneous equation Ax = 0.

1B. Find any/all conditions on b 1 , b 2 and b 3 which are necessary and sufficient for b to be in the span of the set of column vectors of A.

1C. Give the correct definition: What does it mean to say a set of vectors S = {v 1 , v 2 ,... , vp} is linearly independent?

“We say S is linearly independent if and only if... ” [you complete the definition:]

1D. Do the column vectors of A form a linearly independent set? Explain in terms of the definition of linear independence.

1E. Do the column vectors of A span R^3? Explain.

  1. Suppose T : Rk^ → Rq^ is a transformation. Define what it means for T to be a linear transformation.
  2. Suppose T

s 1 s 2 s 3

[

s 12 − s 22 s 1 + s 2 + s 3

]

is a transformation from R^3 → R^2.

Show T is not a linear transformation and in fact fails both parts of the definition in problem (2). In your counterexamples’ vectors, use all-different, positive, single digit numbers for the si’s.

  1. Suppose that T : R^3 → R^4 is a linear transformation and T

 and^ T

5A. Find T

5B. Find T

5C. Let D be the standard matrix of T. How many rows and columns, respectively, does D have?

Number of ROWS: Number of COLUMNS:

5D. Find the last column of D, or explain why you can’t.

5E. Find the first column of D, or explain why you can’t.

  1. For each separate problem below, find a matrix A in RREF (reduced row echelon form) with exactly 3 rows that satisfies the conditions given in the problem. Create your RREF using as few zeros as possible. If there is no such RREF, explain why.

6A. Ax = b has exactly one solution for every b in R^3.

6B. A is the standard matrix of a linear transformation T : R^2 → R^3 and T is onto R^3.

6C. A has 5 columns and some vectors in R^3 are not in the span of those five column vectors.

6D. A is the standard matrix of a linear transformation T : R^4 → R^3 and T is one-to-one.