- #1
Saladsamurai
- 3,020
- 7
...involving Matrix Multiplication... I think it is mainly the notation that is killing me here...but it is killing me.
Problem: Check parts (2) and (3) of theorem (1.3.18) which says:
1. A(BC)=(AB)C
2. A(B+C)=AB+AC
3. (A+B)C=AC+BC
The author led the way on part one with this proof: Let AB=D, BC=G,
(AB)C=F, and A(BC)=H
We must show that F=H.
[tex]d_{ik}=\sum_ja_{ij}b_{jk}[/tex] and [tex]g_{jl}=\sum_kb_{jk}c_{kl}.[/tex]
Hence [tex]f_{il}=\sum_kd_{ik}c_{kl}=\sum_k(\sum_ja_{ij}b_{jk})c_{kl}=(\sum_k\sum_j)a_{ij}b_{jk}c_{kl}[/tex]
=[tex]\sum_ja_{ij}(\sum_kb_{jk}c_{kl})=\sum_ja_{ij}g_{jl}=h_{il}[/tex]
I think I follow that.
It says to use the definition of matrix multiplication as a hint.
Maybe someone could start me off; I am teaching myself this, so it is slow going
Casey
Problem: Check parts (2) and (3) of theorem (1.3.18) which says:
1. A(BC)=(AB)C
2. A(B+C)=AB+AC
3. (A+B)C=AC+BC
The author led the way on part one with this proof: Let AB=D, BC=G,
(AB)C=F, and A(BC)=H
We must show that F=H.
[tex]d_{ik}=\sum_ja_{ij}b_{jk}[/tex] and [tex]g_{jl}=\sum_kb_{jk}c_{kl}.[/tex]
Hence [tex]f_{il}=\sum_kd_{ik}c_{kl}=\sum_k(\sum_ja_{ij}b_{jk})c_{kl}=(\sum_k\sum_j)a_{ij}b_{jk}c_{kl}[/tex]
=[tex]\sum_ja_{ij}(\sum_kb_{jk}c_{kl})=\sum_ja_{ij}g_{jl}=h_{il}[/tex]
I think I follow that.
It says to use the definition of matrix multiplication as a hint.
Maybe someone could start me off; I am teaching myself this, so it is slow going
Casey
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