gainfully employed
grading linear algebra again.
so far this quarter, i’ve (1) returned
the text from last quarter (late) and
i’ve (2) gone back and got a different
copy of the same text a week later.
and that’s it… a week and two days
into the semester.
but starting today there’ll be bigfat
envelopes full of homework piling up
in my mailbox. so very likely i’ll be
posting less over in the cooking show
(where i’ve had a pretty good run going
for about a week).
the livingston review 
September 8, 2014 at 12:14 pm
3. Mark each statement True or False.
You will receive full credit for each correctly marked True statement; however each False statement must also include a counter-example for full credit.
i. Foranytwo3-vectorsuandv,u·v=v·u
ii. Foranytwo3-vectorsuandv,u×v=v×u
iii. Every product of elementary matrices is an elementary matrix.
iv. Every product of elementary matrices is an invertible matrix.
v. If A and B are invertible 2-by-2 matrices, then AB is invertible.
vi. If A and B are invertible 2-by-2 matrices, then A+B is invertible.
vii. Every symmetric matrix is invertible.
viii Every invertible matrix is symmetric.
ix Every system of two equations in two variables has at least one solution.
x Every system of two equations in two variables has at most one solution.