Which of the following statements are true? 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 least one solution.
C. The first entry in the product Ax is a sum of products.
D. The equation Ax = b is consistent if the augmented matrix [Ab] has a pivot position in every row.
E. If the columns of an m \times n matrix A span {\mathbb R}^m, then the equation Ax = b is consistent for each b in {\mathbb R}^m.
F. If A is an m \times n matrix whose columns do not span {\mathbb R}^m, then the equation Ax = b is inconsistent for some b in {\mathbb R}^m.

B, C, E, & F

Step-by-step explanation:

Option A is incorrect because the equation Ax = b is referred to as a matrix equation, not a vector equation.

Option B is correct. If Ax = b has a solution, vector b will a linear combination of columns of matrix A.

Option C is correct. In a matrix equation, product Ax when defined, is a sum of products.

Option D is incorrect. If an augmented matrix [Ab] had a pivot position in every row, there could be a pivot in the last column which would make it inconsistent.

Option E is correct. If the columns of an m×n matrix A span, then the equation Ax=b is consistent for each b in

Option F is correct. IfA is an m x n matrix whose columns do not span, then the equation Ax = b is inconsistent for some b in

Options B, C, E, and F are correct.

hello from mrbilldoesmath!

answer:

25x^2 + 90x + 84

discussion:

mn(x) = m(n(x)) = m( 5x + 9) =

(5x + 9)^2 + 3 =>

25x^2 + 90x + 9^2 + 3 =

25x^2 + 90x + 84                 (as 9^2 = 9*9 = 81)

which is the second choice

regards,  

mrb

p.s.   i'll be on vacation from friday, dec 22 to jan 2, 2019. have a great new year!