Question

matrix question

Answer 1

Evaluate A^3 A= [-1 -2] [ 1 0 ]

Answer 2

Please help if you can :)

Answer 3

You just have to multiply it with it self twice: \[\left[\begin{matrix}-1 & -2 \\ 1 & 0\end{matrix}\right]^3=(\left[\begin{matrix}-1 & -2 \\ 1 & 0\end{matrix}\right]*\left[\begin{matrix}-1 & -2 \\ 1 & 0\end{matrix}\right])*\left[\begin{matrix}-1 & -2 \\ 1 & 0\end{matrix}\right]\]
I assume you know matrix multiplication... if you don't watch this: https://www.khanacademy.org/math/algebra/algebra-matrices/matrix_multiplication/v/matrix-multiplication--part-1

Answer 4

Oh okay that makes sense :) and thanks for the vid.
So, then it would be:
[-1 -8]
[ 1 0]

Answer 5

It is not what i get( http://www.wolframalpha.com/input/?i=%7B%7B-1%2C-2%7D%2C%7B1%2C0%7D%7D%5E3)

Answer 6

Hmm, not sure what i did wrong.

Answer 7

I did -1^3= -1and the same with the rest

Answer 8

that is not how you do matrix multiplication, it is kind og complicatied to explain here, but if you watch the video, you will know what to do :)

Answer 9

Okay thanks.. do you think you can help me figure out this one-

Answer 10

That isn't a question it's just two definitions?

Answer 11

Ah sorry.. i meant to put to find the product of BA

Answer 12

\[B*A=\left[\begin{matrix}4*0+2*-2 & 4*7+2*3 & 4*3+2*0 \\ 1*0-3*-2 & 1*7-3*3 & 1*3-3*0\end{matrix}\right]\]

Answer 13

\[=\left[\begin{matrix}-4 & 34 & 12\\ 6 & -2 & 3\end{matrix}\right]\]