Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**mom****Member**- Registered: 2012-04-25
- Posts: 94

I have:

Let A=[-2 1 3] and B = [0 1 -3]. Find the second row of AB.

1 0 5 1 3 -4

0 4 2 3 0 1

I multiplied and for the second row of AB, I got [15 1 2]

Is this correct?

Offline

**{7/3}****Member**- Registered: 2013-02-11
- Posts: 210

I'm confused,how can 1 by 3 and 1 by 3 matrices be multiplied?

There are 10 kinds of people in the world,people who understand binary and people who don't.

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,061

hi mom,

That's correct.

{7/3} : I think those are two 3 x 3 matrices.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**mom****Member**- Registered: 2012-04-25
- Posts: 94

Please see attached. I have never uploaded in here before but the attachment shows how I did my work.

I know how to go through the process of multiplication for the matrices. I am just not sure that is what the question was asking me to do.

Offline

**mom****Member**- Registered: 2012-04-25
- Posts: 94

Bob,

yes they are two 3 x 3 matrices. So for the second row of AB it would be [15 1 2] ?

It didn't say to multiply so I wasn't sure that I worked the problem correctly but if you have A matrix B matrix and you have to come up with the second row of AB for the matrices, was I correct in assuming that I was to multiply?

Thanks so much.

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,061

Yes; in matrix work AB means A multiplied by B.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**mom****Member**- Registered: 2012-04-25
- Posts: 94

Bob,

thanks so much.

Offline