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Untitled Quiz

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Questions and Answers

What is a linear equation?

  • An equation involving only integers
  • An equation that cannot be solved
  • An equation that can be written as a1x1 + a2x2 +...= b (correct)
  • An equation that has only one variable
  • What defines a consistent system?

  • Has a unique solution
  • Has no solutions
  • Has one or infinitely many solutions (correct)
  • Has an undefined number of solutions
  • What characterizes an inconsistent system?

  • Has infinitely many solutions
  • Has no solution (correct)
  • Has one solution
  • Has a unique solution
  • What is a leading entry?

    <p>Leftmost non-zero entry in a non-zero row</p> Signup and view all the answers

    Describe Echelon form.

    <ol> <li>All nonzero rows are above any all zero rows; 2. Each leading entry is in a column to the right of the previous leading entry; 3. All entries below a leading entry in its column are zeros</li> </ol> Signup and view all the answers

    What is Reduced Echelon Form?

    <p>Same as echelon form, except all leading entries are 1 and each leading 1 is the only non-zero entry in its row.</p> Signup and view all the answers

    What does Span refer to?

    <p>The collection of all vectors in R^n that can be written as c1v1 + c2v2 +...</p> Signup and view all the answers

    What does the equation Ax = b signify?

    <p>Each b is a linear combination of A and has at least one solution for each b in R^n.</p> Signup and view all the answers

    What is a pivot position?

    <p>A position in the original matrix that corresponds to a leading 1 in a reduced echelon matrix.</p> Signup and view all the answers

    Define a pivot column.

    <p>A column that contains a pivot position.</p> Signup and view all the answers

    What does homogeneous refer to in linear systems?

    <p>A system that can be written as Ax = 0.</p> Signup and view all the answers

    What does it mean for columns to be independent?

    <p>If only the trivial solution exists for a linear equation.</p> Signup and view all the answers

    What does dependent signify in linear equations?

    <p>If non-zero weights that satisfy the equation exist.</p> Signup and view all the answers

    What is transformation in linear algebra?

    <p>Assigns each vector x in R^n a vector T(x) in R^m.</p> Signup and view all the answers

    What are Matrix multiplication warnings?

    <ol> <li>AB != BA; 2. If AB = AC, B does not necessarily equal C; 3. If AB = 0, it cannot be concluded that either A or B is equal to 0.</li> </ol> Signup and view all the answers

    What does transposition of a matrix do?

    <p>Flips rows and columns.</p> Signup and view all the answers

    List the Properties of transposition.

    <ol> <li>(A^T)^T = A; 2. (A+B)^T = A^T + B^T; 3. (rA)^T = r<em>A^T; 4. (AB)^T = B^T</em>A^T.</li> </ol> Signup and view all the answers

    What are Invertibility rules?

    <ol> <li>If A is invertible, (A^-1)^-1 = A; 2. (AB)^-1 = B^-1 * A^-1; 3. (A^T)^-1 = (A^-1)^T.</li> </ol> Signup and view all the answers

    What comprises the Invertible Matrix Theorem?

    <p>A is invertible; A is row equivalent to I; A has n pivot columns; Ax = 0 has only the trivial solution; the transformation x --&gt; Ax is one to one; and more.</p> Signup and view all the answers

    What is Column Row Expansion of AB?

    <p>col1Arow1B +...</p> Signup and view all the answers

    What is LU Factorization?

    <ol> <li>Ly = b; Ux = y; 2. Reduce A to echelon form; 3. Place values in L that would reduce it to I.</li> </ol> Signup and view all the answers

    What does the Leontief input-output model represent?

    <p>x = Cx + d.</p> Signup and view all the answers

    What defines Subspaces?

    <ol> <li>The zero vector is in H; 2. For u and v in H, u + v is also in H; 3. For u in H, cu is also in H.</li> </ol> Signup and view all the answers

    What is Column space?

    <p>Set of all the linear combinations of the columns of A.</p> Signup and view all the answers

    What is Null space?

    <p>Set of all solutions to Ax = 0.</p> Signup and view all the answers

    Define a Basis.

    <p>A linearly independent set in H that spans H; the pivot columns of A form a basis for A's column space.</p> Signup and view all the answers

    What is Dimension?

    <p>The number of vectors in any basis of H; the zero subspace's dimension is 0.</p> Signup and view all the answers

    What does rank mean?

    <p>The dimension of the column space.</p> Signup and view all the answers

    What does one-to-one mean in transformations?

    <p>A transformation that assigns a vector y in R^m for each x in R^n; there's a pivot in every column.</p> Signup and view all the answers

    What does onto mean in linear transformations?

    <p>Consistent for any b; pivots in all rows.</p> Signup and view all the answers

    What is an inner product?

    <p>A matrix product u^Tv or u.v where u and v are vectors.</p> Signup and view all the answers

    Define orthogonal component.

    <ol> <li>x is in W' if x is perpendicular to every vector that spans W; 2. W' is a subspace of R^n.</li> </ol> Signup and view all the answers

    What is an orthogonal set?

    <p>A set of vectors where u_i.u_j = 0 (and i != j).</p> Signup and view all the answers

    What does orthonormal mean?

    <p>An orthogonal set of unit vectors.</p> Signup and view all the answers

    Study Notes

    Linear Algebra Concepts

    • Linear Equation: Formulated as a1x1 + a2x2 + ... = b; coefficients a1, a2, etc. can be real or complex numbers known beforehand.

    • Consistent System: A linear system with at least one solution; can have one or infinitely many solutions.

    • Inconsistent System: A system that does not have any solutions.

    • Leading Entry: The first non-zero element in a non-zero row of a matrix.

    • Echelon Form: Matrix characteristics include: all non-zero rows above any zero rows; each leading entry appears in a new column to the right; all elements below a leading entry are zeros.

    • Reduced Echelon Form: An extension of echelon form where leading entries are '1' and each leading '1' is the only non-zero element in its row; each matrix has a unique reduced echelon form.

    Vector Spaces and Transformations

    • Span: The set of all possible linear combinations formed from vectors in R^n, expressed as c1v1 + c2v2 + ... (where ci are constants).

    • Ax = b: For each vector b in R^n, this equation has a solution if the following are true: each b is a linear combination of A, the columns of A span R^n, and A has a pivot position in every row.

    • Pivot Position: Highlighted by a leading '1' in a reduced echelon matrix, located in the original matrix.

    • Pivot Column: A column that has a pivot position which plays a critical role in the structure of the linear transformation.

    Systems of Equations and Solutions

    • Homogeneous System: Defined by Ax = 0 where the trivial solution x = 0 is guaranteed.

    • Independent Vectors: Vectors that provide only the trivial solution when forming a linear combination; columns of A are independent if only the trivial solution exists.

    • Dependent Vectors: Exist when non-zero weights can satisfy the equation; more vectors than entries indicates dependency.

    Matrix Operations

    • Transformation: A function that maps vectors from R^n to vectors in R^m.

    • Matrix Multiplication Properties: Important facts include AB ≠ BA, if AB = AC, B may not equal C, and the product AB = 0 does not mean A or B is zero.

    • Transposition: Involves exchanging rows and columns of a matrix.

    Fundamental Matrix Theorems

    • Properties of Transposition: Key properties include (A^T)^T = A, (A + B)^T = A^T + B^T, scalar multiplication (rA)^T = rA^T, and the rule for products (AB)^T = B^T A^T.

    • Invertibility Rules: Encompass conditions such as if A is invertible, then (A^-1)^-1 = A; for multiplied matrices (AB)^-1 = B^-1 A^-1; and transpose invertibility (A^T)^-1 = (A^-1)^T.

    • Invertible Matrix Theorem: States conditions where a matrix A is invertible. If any condition is true, all are true: A is row equivalent to I, has n pivot columns, Ax = 0 has only the trivial solution, and spans R^n.

    Linear Spaces and Properties

    • Column Space: Composed of all linear combinations derived from the columns of matrix A.

    • Null Space: The set of solutions to the equation Ax = 0.

    • Basis: A linearly independent set that spans H; pivot columns of A form a basis for A's column space.

    • Dimension: Indicates the number of vectors in any basis for the subspace H; the dimension of the zero subspace is defined as 0.

    • Rank: Represents the dimension of a matrix’s column space.

    Transformations and Their Characteristics

    • One-to-One Transformation: A transformation where each vector y in R^m corresponds to one unique x in R^n, necessitating a pivot in every column.

    • Onto Transformation: A transformation that is consistent for any vector b, requiring pivots in all rows.

    Orthogonality Concepts

    • Inner Product: Denotes a matrix product u^T v or the dot product u.v; if the result is 0, the vectors u and v are orthogonal.

    • Orthogonal Component: Defined as x being in W' if it is perpendicular to every vector spanning W; W' forms a subspace in R^n.

    • Orthogonal Set: A collection of vectors where each pair of different vectors is orthogonal (i.e., their inner product equals zero); guarantees linear independence and forms a basis of the subspace.

    • Orthonormal Set: A set of vectors that are both orthogonal and unit vectors.

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