(linear algebra)
1. (5 points) Indicate whether each of the following statements
are (T) true or (F) false.
(a) T or F. If the set {u, v, w} is linearly independent, then u, v,
and w are not in R2.
(b) T or F. If T(x) = Ax, R(y) = By, and the composition R ◦ T is defined,
then R ◦ T(x) = BAx.
(c) T or F. If the set {u, v, w, x} spans Rm, then m ≤ 4.
(d) T or F. Any set of vectors containing 0 is linearly dependent,
including the set {0}.
(e) T or F. If T is a matrix transformation, then T(0) = 0.
2. (10 points) Complete the following statement by selecting all
options that apply.
The columns of an m × n matrix A span Rm if ...
(A) A has m pivot columns (a pivot in every row).
(B) A has n pivot columns (a pivot in every column).
(C) the equation Ax = 0 has only the trivial solution.
(D) the equation Ax = 0 has nontrivial solutions.
(E) for each b in Rm, the equation Ax = b has a solution.
(F) there exists a b in Rm such that the equation Ax = b is
inconsistent.
(G) the associated system of equations has at least one free
variable.
(H) the associated system of equations has no free variables.
(I) each b in Rm is a linear combination of the columns of A.
(J) there exists a b in Rm that is not a linear combination of the
columns of A.
3. (6 points) Let u = [8, 19], v = [4, 7], and w = [3, 5].
(a) Write u as a linear combination of v and w (find scalars a and b
so that u = av + bw).
(b) Does the set {u, v, w} span R2?
4. (6 points) Let T : R2 → R3 be a matrix transformation such
that
T(x) = [x1 - 3x2, x1 - x2, 3x1 - 4x2].
(a) Find a matrix A such that T(x) = Ax for each x in R2.
(b) Find an x in R2 such that T(x) = [3, 7, 14].
5. (12 points) Let T : R2 → R2 be a matrix transformation
satisfying
T([1, 0]) = [2, 1] and T([4, 3]) = [8, 2].
(a) What is T([5, 3])?
(b) What is T([0, 1])?
(c) Find a 2 × 2 matrix A for which T(x) = Ax.
(d) What is T ◦ T ◦ T ◦ T([1, 0])?