Matrices

I'm of no help my friend; 'attachments not found' :')

I'm of no help my friend; 'attachments not found' :'

$\begin{pmatrix} 2 & a \\ 1 & 3 \end{pmatrix} \begin{pmatrix} a \\ b \end{pmatrix} = \begin{pmatrix} -1 \\ 2 \end{pmatrix}$

I multiplied them together and got:

$\begin{pmatrix} 2a+ab \\ a-3b \end{pmatrix} = \begin{pmatrix} -1 \\ 2 \end{pmatrix}$

$2a + ab = -1$
$a - 3b = 2$

Whats the question? Attachment still unavailable.

You have simultaneous equations so try rearranging the second equation in terms of a then substituting it into the top equation

$\begin{pmatrix} 2 & a \\ 1 & 3 \end{pmatrix} \begin{pmatrix} a \\ b \end{pmatrix} = \begin{pmatrix} -1 \\ 2 \end{pmatrix}$

I multiplied them together and got:

$\begin{pmatrix} 2a+ab \\ a-3b \end{pmatrix} = \begin{pmatrix} -1 \\ 2 \end{pmatrix}$

$2a + ab = -1$
$a - 3b = 2$

Yeah I know its simultaneous equations, but I don't get what you're saying.

$a = 2 + 3b$ ?

Rearrange for A, sub A in to the top equation is what they are meaning I think. Do you know how to calculate the inverse of a matrix?

$\begin{pmatrix} 2 & a \\ 1 & 3 \end{pmatrix} \begin{pmatrix} a \\ b \end{pmatrix} = \begin{pmatrix} -1 \\ 2 \end{pmatrix}$

I multiplied them together and got:

Where does the - 3b come from?

Oh **** sorry, its meant to say -3 not 3 in the question

No xD. I've only had two lessons on them, and we have mainly been doing multiplying matrices and a few simultaneous equations with matrices

Where does the - 3b come from?

Then they'll want you to substitute in for a and rearrange

Factorize and make "a" the subject of the first equation.
Then, substitute this into the second one, and solve for "b".
Or make "b" the subject in the second one, and substitute into first one.

There are other ways as well. It's basically a simultaneous equation

You have simultaneous equations so try rearranging the second equation in terms of a then substituting it into the top equation