# Math Help - matrix help

1. ## matrix help

if r1 = [ 3 + 4j
1 - 2j]

and r2 = [ 1 - j
5 + 5j]

both r1 and r2 being (1 x 2)matrices not (2 x 1)matrices as i dunno how to do proper matrices

how would i work out

(r1.r2) $^(-1)$

2. Originally Posted by mathmonster
if r1 = [ 3 + 4j
1 - 2j]

and r2 = [ 1 - j
5 + 5j]

both r1 and r2 being (1 x 2)matrices not (2 x 1)matrices as i dunno how to do proper matrices

how would i work out

(r1.r2) $^(-1)$
Matrix multiplication between two matrices of dimension (2x1) (and as posted they ARE (2x1): 2 rows and 1 column) is not defined so r1.r2 is not defined. Your question as posted is fatally flawed.

Aside: Matrix multiplication between two matrices of dimension (1x2) is also not defined.