That comment was from my Algebra 2 class on Friday when trying to discuss the idea of a function being “one to one”.

The only thing I said was, “For every ‘x’ there is only one ‘y’ and for every ‘y’ there is only one ‘x’.” And one of my ditzy cheerleaders became wide-eyed with understanding and blurted that out.

Thought that was kind of cool–>and I’m stealing it for future discussions.

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Hi there. Found you from your comment at Teaching Statistics.I’m getting ready to introduce the idea of functions to one class and may well steal this quote. My concern is that every x only matches up with one y, but the y can match up with multiple x’s (parabola, sine, cosine…). How did you end up dealing with that?

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Well, the idea of a function reads just like you said – each x can only match up with one y. I talk about that like guys are the “x” and girls are the “y”. Guys are supposed to pine away after only one girl at a time. But us GIRLS may allow as many suitors as we want at one time (to find the RIGHT guy for us). This worked well at the middle school level and with my younger students at the high school. However, some students might be (honestly) thinking “slut” if you introduce it that way. So you might want to turn it around and say that girls are dedicated and honest, so they only fall in love with one guy at a time (the girls being “x”). But GUYS are ruthless and awful, so they’ll have multiple girlfriends at one time (the guys being “y”). For some sexist reason, this is more acceptable for guys to be huge flirts.The “soul mates” thing only applies if a function is one-to-one (i.e. it must pass the horizontal AND vertical line test). That’s what makes them special.Thanks for the comment!

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