(4) Let A be an invertible matrix. Prove that if A = Q¸R1 decompositions of A and if the diagonal entries of R1 and R2 are positive, then Q1 R1 = R2. = Q¿R2 are two QR- = Q2 and

8) Let A be an nxn ma triX. vector b the equation Ax = b has more than one solution. Explain why A is not an invertible Matrix.

|X= 3 -2 -2 2 ဦး + 0 1 + --L 1 Find a Basis for Column B of this Matrix

Let A B denotes the tensor product of matrices Amxn and Bpxq defined by the block matrix A B = a12B 922B a11B a21 B : : ami B am2 B : ain B a2n B : amn B mpxnq (a) Let A, B, C, D be defined as Amxn, Bpxq, Cnxk, and Dqxr. Prove that (AB)(C > D) = ACⒸ BD (b) Let Amxm and B₁xn be nonsingular matrices. - Prove that (AB) is nonsingular. - Find the inverse matrix of (AB) (c) Prove that the following equality applies for any Amxm and Bnxn square matrices trace(AB) = trace(A) * trace(B)

The set of non-zero vectors {b,, b,, bz, b4} are vectors in R* with the property that 4b, + 2b, = 6b, . Let matrix B = | b, b2 b; b4. (a) What does the matrix b, b, b, reduce to in RREF form? (b) Find a specific solution to the matrix equation Bx = 0. That is, find an x vector that solves that equation. (c) What is the maximum number of pivots matrix B can have? Please explain briefly referencing anything from above. (d) Can the set of vectors {b1, b2, b3, b4} span R’? Explain why or why not? (e) Can the set of vectors {b,, b2, b3, b4} span R*? Explain why or why not? (f) Matrix M is 7 x 4. If possible, show that the columns of the matrix MB are linearly dependent. If it is not possible to show this, explain why.