Question 23: Mark each statement True or False. Justify each answer.

a. The equation\(Ax = b\)is referred to as a vector equation.

b. A vector\(b\)is a linear combination of the columns of a matrix A if and only if the equation\(Ax = b\)has at leastone solution.

c. The equation\(Ax = b\)is consistent if the augmented matrix\(\left[ {\begin{array}{*{20}{c}}A&b\end{array}} \right]\)has a pivot position in every row.

d. The first entry in the product\(Ax\)is a sum of products.

e. If the columns of an\(m \times n\)matrix A span\({R^m}\), then the equation\(Ax = b\)is inconsistent for some b in\({R^m}\).

f. If A is an \(m \times n\) matrix and if the equation \(Ax = b\)is inconsistent for some b in \({R^m}\), then A cannot have a pivotposition in every row.

Short Answer

Expert verified

a. False

b. True

c. False

d. True

e. True

f. True

Step by step solution

01

(a)

The equation \(Ax = b\) is known as the matrix equation.

Hence, the given statement is false.

02

(b)

According to the existence of the solutions, If and only if b is a linear combination of A's column, then the equation \(Ax = b\) has a solution.

Hence, the given statement is true.

03

(c)

The equation \(Ax = b\) may or may not be consistent if an augmented matrix \(\left[ {\begin{array}{*{20}{c}}A&b\end{array}} \right]\) has a pivot position in every row.

Hence, the given statement is false.

04

(d)

The row vector rule states that the sum of the products of comparable elements from row \(i\) of A and from vector x equals the \(ith\) entry in \(Ax\) if the product \(Ax\) is specified.

Hence, the given statement is true.

05

(e)

Assume A is a \(m \times n\) matrix.Then,

a. The equation \(Ax = b\) has a solution for each b in \({R^m}\).

b. \({R^m}\) is spanned by the columns of A.

Hence, the given statement is true.

06

(f)

Assume A is a \(m \times n\) matrix. Thus, the propositions that follow are logically equivalent if:

a. The equation \(Ax = b\) has a solution for each b in \({R^m}\).

b. In each row, A has a pivot position.

Hence, the given statement is true.

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