How do you multiply #((1, 3))# with #((-1, 2, 2, 4))#?

1 Answer
Apr 20, 2016

You can't.

Explanation:

Perhaps one of the following was intended:

Possibility 1
Multiply #((1,3))# by #((-1,2),(2,4))#
Remember we multiply "rows" by "columns"
There is only one row: #((1,3))#
but two columns: #((-1),(2))# and #((2),(4))#

#((1,3))xx((-1,2),(2,4))#

#color(white)("XXX") = ((1xx(-1)+2xx2,1xx2+3xx4))#

#color(white)("XXX")=((3,14))#

Possibility 2
Multiply #((1),(3))# by #((-1,2,2,4))#
I've left this one undone since I think it is less likely to be what is intended.

Remember:
For matrix multiplication,
#color(white)("XXX")#the number of entries in each row that you are multiplying
#color(white)("XXXXXX")#must be equal to
#color(white)("XXX")#the number of entries in each column that you are multiplying by