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Math Algebra Linear Algebra and Its Applications (5th Edition)

Let A be an m × n matrix. Use the steps below to show that a vector x in ℝ n satisfies A x = 0 if and only if A T A x = 0 . This will show that Nul A = Nul A T A . a. Show that if A x = 0 , then A T A x = 0 . b. Suppose A T A x = 0 . Explain why x T A T A x = 0 , and use this to show that A x = 0 .

Let A be an m × n matrix. Use the steps below to show that a vector x in ℝ n satisfies A x = 0 if and only if A T A x = 0 . This will show that Nul A = Nul A T A . a. Show that if A x = 0 , then A T A x = 0 . b. Suppose A T A x = 0 . Explain why x T A T A x = 0 , and use this to show that A x = 0 .

Solution Summary: The author illustrates how the vector x in Rn satisfies the value of ATextx=0 using the steps.

Linear Algebra and Its Applications (5th Edition)

Linear Algebra and Its Applications (5th Edition)

5th Edition

ISBN: 9780321982384

Author: David C. Lay, Steven R. Lay, Judi J. McDonald

Publisher: PEARSON

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Textbook Question

Chapter 6.5, Problem 19E

Let A be an m × n matrix. Use the steps below to show that a vector x in ℝⁿ satisfies Ax = 0 if and only if A^TAx = 0. This will show that Nul A = Nul A^TA.

a. Show that if Ax = 0, then A^TAx = 0.
b. Suppose A^TAx = 0. Explain why x^TA^TAx = 0, and use this to show that Ax = 0.

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Chapter 6.5, Problem 18E

Chapter 6.5, Problem 20E

Chapter 6 Solutions

Linear Algebra and Its Applications (5th Edition)

Ch. 6.1 - Let a = [21] and b = [31]. Compute abaa and...Ch. 6.1 - Let c = [4/312/3] and d = [561]. a. Find a unit...Ch. 6.1 - Let W be a subspace of Rn. Exercise 30 establishes...Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - Compute the quantities in Exercises 18 using the...

Ch. 6.1 - Compute the quantities in Exercises 18 using the...Ch. 6.1 - In Exercises 912, find a unit vector in the...Ch. 6.1 - In Exercises 912, find a unit vector in the...Ch. 6.1 - In Exercises 912, find a unit vector in the...Ch. 6.1 - Prob. 12E Ch. 6.1 - Find the distance between x = [103] and y = [15].Ch. 6.1 - Find the distance between u = [052] and z = [418].Ch. 6.1 - Determine which pairs of vectors in Exercises 1518...Ch. 6.1 - Determine which pairs of vectors in Exercises 1518...Ch. 6.1 - Determine which pairs of vectors in Exercises 1518...Ch. 6.1 - Determine which pairs of vectors in Exercises 1518...Ch. 6.1 - In Exercises 19 and 20, all vectors are in n. Mark...Ch. 6.1 - In Exercises 19 and 20, all vectors are in n. Mark...Ch. 6.1 - Use the transpose definition of the inner product...Ch. 6.1 - Prob. 22E Ch. 6.1 - Let u = [251] and v = [746]. Compute and compare...Ch. 6.1 - Verify the parallelogram law for vectors u and v...Ch. 6.1 - Let v = [ab] Describe the set H of vectors [xy]...Ch. 6.1 - Let u = [567], and let W be the set of all x in 3...Ch. 6.1 - Suppose a vector y is orthogonal to vectors u and...Ch. 6.1 - Suppose y is orthogonal to u and v. Show that y is...Ch. 6.1 - Let W = Span {v1,,vp}. Show that if x is...Ch. 6.1 - Let W be a subspace of n, and let W be the set of...Ch. 6.1 - Show that if x is in both W and W, then x = 0.Ch. 6.2 - Let u1= [1/52/5] and u2= [2/51/5]. Show that {u1....Ch. 6.2 - Let y and L be as in Example 3 and Figure 3....Ch. 6.2 - Let U and x be as in Example 6. and let y = [326]....Ch. 6.2 - Let U be an n n matrix with orthonormal columns....Ch. 6.2 - In Exercises 16, determine which sets of vectors...Ch. 6.2 - In Exercises 16, determine which sets of vectors...Ch. 6.2 - In Exercises 16, determine which sets of vectors...Ch. 6.2 - In Exercises 16, determine which sets of vectors...Ch. 6.2 - In Exercises 16, determine which sets of vectors...Ch. 6.2 - In Exercises 16, determine which sets of vectors...Ch. 6.2 - In Exercises 710, show that {u1, u2} or {u1, u2,...Ch. 6.2 - In Exercises 710, show that {u1, u2} or {u1, u2,...Ch. 6.2 - In Exercises 710, show that {u1, u2} or {u1, u2,...Ch. 6.2 - In Exercises 710, show that {u1, u2} or {u1, u2,...Ch. 6.2 - Compute the orthogonal projection of [17] onto the...Ch. 6.2 - Compute the orthogonal projection of [11] onto the...Ch. 6.2 - Let y = [23] and u = [47] Write y as the sum of...Ch. 6.2 - Let y = [26] and u = [71] Write y as the sum of a...Ch. 6.2 - Let y = [31] and u = [86] Compute the distance...Ch. 6.2 - Let y = [39] and u = [12] Compute the distance...Ch. 6.2 - In Exercises 1722, determine which sets of vectors...Ch. 6.2 - In Exercises 1722, determine which sets of vectors...Ch. 6.2 - In Exercises 1722, determine which sets of vectors...Ch. 6.2 - In Exercises 1722, determine which sets of vectors...Ch. 6.2 - In Exercises 1722, determine which sets of vectors...Ch. 6.2 - In Exercises 1722, determine which sets of vectors...Ch. 6.2 - In Exercises 23 and 24, all vectors are in n. Mark...Ch. 6.2 - In Exercises 23 and 24, all vectors are in n. Mark...Ch. 6.2 - Prove Theorem 7. [Hint: For (a), compute |Ux||2,...Ch. 6.2 - Suppose W is a sub space of n spanned by n nonzero...Ch. 6.2 - Let U be a square matrix with orthonormal columns....Ch. 6.2 - Let U be an n n orthogonal matrix. Show that the...Ch. 6.2 - Let U and V be n n orthogonal matrices. Explain...Ch. 6.2 - Let U be an orthogonal matrix, and construct V by...Ch. 6.2 - Show that the orthogonal projection of a vector y...Ch. 6.2 - Let {v1, v2} be an orthogonal set of nonzero...Ch. 6.2 - Prob. 33E Ch. 6.2 - Given u 0 in n, let L = Span{u}. For y in n, the...Ch. 6.3 - Let u1 = [714], u2 = [112], x = [916], and W =...Ch. 6.3 - Let W be a subspace of n. Let x and y be vectors...Ch. 6.3 - In Exercises 1 and 2, you may assume that {u1,,...Ch. 6.3 - u1 = [1211], u2 = [2111], u3 = [1121], u4 =...Ch. 6.3 - In Exercises 36, verify that {u1, u2} is an...Ch. 6.3 - In Exercises 36, verify that {u1, u2} is an...Ch. 6.3 - In Exercises 36, verify that {u1, u2} is an...Ch. 6.3 - In Exercises 36, verify that {u1, u2} is an...Ch. 6.3 - In Exercises 710, let W be the subspace spanned by...Ch. 6.3 - In Exercises 710, let W be the subspace spanned by...Ch. 6.3 - In Exercises 710, let W be the subspace spanned by...Ch. 6.3 - In Exercises 710, let W be the subspace spanned by...Ch. 6.3 - In Exercises 11 and 12, find the closest point to...Ch. 6.3 - In Exercises 11 and 12, find the closest point to...Ch. 6.3 - In Exercises 13 and 14, find the best...Ch. 6.3 - In Exercises 13 and 14, find the best...Ch. 6.3 - Let y = [595], u1 = [351], u2 = [321]. Find die...Ch. 6.3 - Let y, v1, and v2 be as in Exercise 12. Find the...Ch. 6.3 - Let y = [481], u1 = [2/31/32/3], u2 = [2/32/31/3],...Ch. 6.3 - Let y = [79], u1 = [1/103/10], and W = Span {u1}....Ch. 6.3 - Let u1 = [112], u2 = [512], and u3 = [001].Note...Ch. 6.3 - Let u1 and u2 be as in Exercise 19, and let u4 =...Ch. 6.3 - In Exercises 21 and 22, all vectors and subspaces...Ch. 6.3 - In Exercises 21 and 22, all vectors and subspaces...Ch. 6.3 - Let A be an m m matrix. Prove that every vector x...Ch. 6.3 - Let W be a subspace of n with an orthogonal basis...Ch. 6.4 - Let W = Span {x1, x2}, where x1 = [111] and x2 =...Ch. 6.4 - Suppose A = QR, where Q is an m n matrix with...Ch. 6.4 - In Exercises 1-6, the given set is a basis for a...Ch. 6.4 - In Exercises 1-6, the given set is a basis for a...Ch. 6.4 - In Exercises 1-6, the given set is a basis for a...Ch. 6.4 - In Exercises 1-6, the given set is a basis for a...Ch. 6.4 - In Exercises 1-6, the given set is a basis for a...Ch. 6.4 - In Exercises 1-6, the given set is a basis for a...Ch. 6.4 - Find an orthonormal basis of the subspace spanned...Ch. 6.4 - Find an orthonormal basis of the subspace spanned...Ch. 6.4 - Find an orthogonal basis for the column space of...Ch. 6.4 - Find an orthogonal basis for the column space of...Ch. 6.4 - Find an orthogonal basis for the column space of...Ch. 6.4 - Find an orthogonal basis for the column space of...Ch. 6.4 - In Exercises 13 and 14, the columns of Q were...Ch. 6.4 - In Exercises 13 and 14, the columns of Q were...Ch. 6.4 - Find a QR factorization of the matrix in Exercise...Ch. 6.4 - Find a QR factorization of the matrix in Exercise...Ch. 6.4 - In Exercises 17 and 18, all vectors and subspaces...Ch. 6.4 - In Exercises 17 and 18, all vectors and subspaces...Ch. 6.4 - Suppose A = QR, where Q is m n and R is n n....Ch. 6.4 - Suppose A = QR, where R is an invertible matrix....Ch. 6.4 - Given A = QR as in Theorem 12, describe how to...Ch. 6.4 - Let u1, , up be an orthogonal basis for a subspace...Ch. 6.4 - Suppose A = QR is a QR factorization of an m n...Ch. 6.4 - [M] Use the Gram-Schmidt process as in Example 2...Ch. 6.4 - [M] Use the method in this section to produce a QR...Ch. 6.5 - Let A = [133151172] and b = [535]. Find a...Ch. 6.5 - What can you say about the least-squares solution...Ch. 6.5 - In Exercises 1-4, find a least-squares solution of...Ch. 6.5 - In Exercises 1-4, find a least-squares solution of...Ch. 6.5 - In Exercises 1-4, find a least-squares solution of...Ch. 6.5 - In Exercises 1-4, find a least-squares solution of...Ch. 6.5 - In Exercises 5 and 6, describe all least-squares...Ch. 6.5 - In Exercises 5 and 6, describe all least-squares...Ch. 6.5 - Compute the least-squares error associated with...Ch. 6.5 - Compute the least-squares error associated with...Ch. 6.5 - In Exercises 9-12, find (a) the orthogonal...Ch. 6.5 - In Exercises 9-12, find (a) the orthogonal...Ch. 6.5 - In Exercises 9-12, find (a) the orthogonal...Ch. 6.5 - In Exercises 9-12, find (a) the orthogonal...Ch. 6.5 - Let A = [342134], b = [1195], u = [51], and v =...Ch. 6.5 - Let A = [213432], b = [544], u = [45], and v =...Ch. 6.5 - In Exercises 15 and 16, use the factorization A =...Ch. 6.5 - In Exercises 15 and 16, use the factorization A =...Ch. 6.5 - In Exercises 17 and 18, A is an m n matrix and b...Ch. 6.5 - a. If b is in the column space of A, then every...Ch. 6.5 - Let A be an m n matrix. Use the steps below to...Ch. 6.5 - Let A be an m n matrix such that ATA is...Ch. 6.5 - Let A be an m n matrix whose columns are linearly...Ch. 6.5 - Use Exercise 19 to show that rank ATA = rank A....Ch. 6.5 - Suppose A is m n with linearly independent...Ch. 6.5 - Find a formula for the least-squares solution of...Ch. 6.5 - Describe all least-squares solutions of the system...Ch. 6.6 - When the monthly sales of a product are subject to...Ch. 6.6 - In Exercises 1-4, find the equation y = 0 + 1x of...Ch. 6.6 - In Exercises 1-4, find the equation y = 0 + 1x of...Ch. 6.6 - In Exercises 1-4, find the equation y = 0 + 1x of...Ch. 6.6 - In Exercises 1-4, find the equation y = 0 + 1x of...Ch. 6.6 - Let X be the design matrix used to find the...Ch. 6.6 - Let X be the design matrix in Example 2...Ch. 6.6 - A certain experiment produces the data (1, 7.9),...Ch. 6.6 - Let x=1n(x1++xn) and y=1n(y1++yn). Show that the...Ch. 6.6 - Derive the normal equations (7) from the matrix...Ch. 6.6 - Use a matrix inverse to solve the system of...Ch. 6.6 - a. Rewrite the data in Example 1 with new...Ch. 6.6 - Suppose the x-coordinates of the data (x1, y1), ,...Ch. 6.6 - Exercises 19 and 20 involve a design matrix X with...Ch. 6.6 - Show that X2=TXTy. [Hint: Rewrite the left side...Ch. 6.7 - Use the inner product axioms to verify the...Ch. 6.7 - Use the inner product axioms to verify the...Ch. 6.7 - Let 2 have the inner product of Example 1, and let...Ch. 6.7 - Let 2 have the inner product of Example 1. Show...Ch. 6.7 - Exercises 3-8 refer to 2 with the inner product...Ch. 6.7 - Exercises 3-8 refer to 2 with the inner product...Ch. 6.7 - Exercises 3-8 refer to 2 with the inner product...Ch. 6.7 - Exercises 3-8 refer to 2 with the inner product...Ch. 6.7 - Exercises 3-8 refer to 2 with the inner product...Ch. 6.7 - Exercises 3-8 refer to 2 with the inner product...Ch. 6.7 - Let 3 have the inner product given by evaluation...Ch. 6.7 - Let 3 have the inner product as in Exercise 9,...Ch. 6.7 - Let p0, p1, and p2 be the orthogonal polynomials...Ch. 6.7 - Find a polynomial p3 such that {p0, p1, p2, p3}...Ch. 6.7 - Let A be any invertible n n matrix. Show that for...Ch. 6.7 - Let T be a one-to-one linear transformation from a...Ch. 6.7 - Use the inner product axioms and other results of...Ch. 6.7 - Use the inner product axioms and other results of...Ch. 6.7 - Use the inner product axioms and other results of...Ch. 6.7 - Use the inner product axioms and other results of...Ch. 6.7 - Given a 0 and b 0, let u=[ab] and v=[ba]. Use...Ch. 6.7 - Let u=[ab] and v=[11]. Use the Cauchy-Schwarz...Ch. 6.7 - Exercises 21-24 refer to V = C[0, 1], with the...Ch. 6.7 - Exercises 21-24 refer to V = C[0, 1], with the...Ch. 6.7 - Compute f for f in Exercise 21. Exercises 21-24...Ch. 6.7 - Compute g for g in Exercise 22. Exercises 21-24...Ch. 6.7 - Let V be the space C[1, 1] with the inner product...Ch. 6.7 - Let V be the space C[2, 2] with the inner product...Ch. 6.8 - Let q1(t) = 1, q2(t) = t, and q3(t) = 3t2 4....Ch. 6.8 - Find the first-order and third-order Fourier...Ch. 6.8 - Find the least-squares line y = 0 + 1x that best...Ch. 6.8 - Suppose 5 out of 25 data points in a weighted...Ch. 6.8 - Fit a cubic trend function to the data in Example...Ch. 6.8 - To make a trend analysis of six evenly spaced data...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - Prob. 7E Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - In Exercises 5-14, the space is C[0, 2] with the...Ch. 6.8 - [M] Refer to the data in Exercise 13 in Section...Ch. 6.8 - [M] Let f4 and f5 be the fourth-order and...Ch. 6 - Prob. 1SE Ch. 6 - Prob. 2SE Ch. 6 - Let {v1, , vp} be an orthonormal set in n. Verify...Ch. 6 - Let U be an n n orthogonal matrix. Show that if...Ch. 6 - Show that if an n n matrix U satisfies (Ux) (Uy)...Ch. 6 - Show that if U is an orthogonal matrix, then any...Ch. 6 - A Householder matrix, or an elementary reflector,...Ch. 6 - Let T: n n be a linear transformation that...Ch. 6 - Let u and v be linearly independent vectors in n...Ch. 6 - Suppose the columns of A are linearly independent....Ch. 6 - If a, b, and c are distinct numbers, then the...Ch. 6 - Consider the problem of finding an eigenvalue of...Ch. 6 - Use the steps below to prove the following...Ch. 6 - Explain why an equation Ax = b has a solution if...Ch. 6 - Exercises 15 and 16 concern the (real) Schur...Ch. 6 - Let A be an n n matrix with n real eigenvalues,...

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