## General Question # Matrices to solve a vector combination problem.

Asked by dotlin (422 ) August 10th, 2010

So I’m just starting out learning this at home.

Lets say we have two vectors

a=[3/-6] <6 below the 3 b=[2/6] again the 6 is below.

a+b=c =[7/6]

Then the book goes off into saying

ax+by=c but in matrix form, there’s a graph of a, b and c next to it and I know x in ax is suppose to be the x coordinates and y is the y coordinates, but what x and y coordinates?

[3/-6]x+[2/6]y=[7/6]

[3/-6]x+[2/6]y= [3, 2/-6, 6][x/y]

the book says 3 x X = 7 but when did we work out what x was and the same with y

Observing members: 0 Composing members: 0  I am completely confused by your notation…

lilikoi (10084 )“Great Answer” (0 ) Flag as…  Your very first equation doesn’t make sense. In Matrix Addition, the sum matrix is comprised of the sums of the corresponding elements of the original matrices.

`|3| |2| |5|`
`| |+| |=| |`
`|-6||6| |0|`

That is, the matrix of 3 over -6 plus the matrix of 2 over 6 equals the matrix of 5 over 0, not 7 over 6.

MrItty (17381 )“Great Answer” (1 ) Flag as…  X=1
Y=2

SolsticeRG (76 )“Great Answer” (0 ) Flag as…  That is, assuming you’ve simply represented linear simultaneous equations:

3X + 2Y = 7
-6X + 6Y = 6,

which can we rewritten in matrix form:

| 3 2 | |X| = |7|
|-6 6 | |Y| = |6|, where this is basically in the form: [A][B] = [C].

Rewriting, you can use inv[A][C] = [B], which solves the linear system using inverse matrices.

A much easier way to do this is through simple elimination (or even substitution). For instructions on that, please see 7th Grade.

SolsticeRG (76 )“Great Answer” (0 ) Flag as… or