Tag Archives: intuition

Test your intuition: bijections

Posted on March 3, 2020 by Brent

Suppose we have sets and and a function (that is, ’s domain is and its codomain is ). Suppose there is another function such that for every . Is necessarily a bijection? That is, does necessarily match up each element … Continue reading →

Posted in logic | Tagged , , , | 12 Comments

Minus times minus is plus

Posted on September 29, 2009 by Brent

I’ve seen several recent posts wondering about an intuitive explanation for the fact that “a minus times a minus equal to a plus”. I understand why people would wonder about this—the way it’s often taught, it seems to be just … Continue reading →

Posted in arithmetic | Tagged , , | 14 Comments

Carnival of Mathematics and other links

Posted on January 18, 2009 by Brent

The 47th Carnival of Mathematics has been put together by jd2718; go give it a read! Some of my favorite posts include factoring by puzzles, teaching binary numbers, the 2009 game, cliques of dichotomies, but there is lots of other … Continue reading →

Posted in links | Tagged , , , | 1 Comment