tag:blogger.com,1999:blog-7691251033406320222.post3826152469820294744..comments2024-03-26T04:19:38.862-07:00Comments on kitchen table math, the sequel: another test - U. WashCatherine Johnsonhttp://www.blogger.com/profile/03347093496361370174noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-7691251033406320222.post-61414344870093934612010-03-16T16:40:14.563-07:002010-03-16T16:40:14.563-07:00Solve for x works if you put the parentheses in: y...Solve for x works if you put the parentheses in: y=x/(x-1)<br /><br />LSquaredAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-75685666640071498722010-03-16T12:36:44.416-07:002010-03-16T12:36:44.416-07:00hmmm... it says "solve for x"hmmm... it says "solve for x"Catherine Johnsonhttps://www.blogger.com/profile/03347093496361370174noreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-16118187498467584662010-03-16T12:35:49.209-07:002010-03-16T12:35:49.209-07:00Did I write that wrong?
Probably.Did I write that wrong?<br /><br />Probably.Catherine Johnsonhttps://www.blogger.com/profile/03347093496361370174noreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-35753074158420747382010-03-15T18:41:18.969-07:002010-03-15T18:41:18.969-07:00You're right; you just need to further simplif...You're right; you just need to further simplify:<br /><br />[-y/(1-y)] * (-1/-1) = x<br /><br />y/(y-1) = xVickyShttps://www.blogger.com/profile/01379636377049707525noreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-72501084460636872342010-03-15T09:17:20.640-07:002010-03-15T09:17:20.640-07:00OK, I'll try it. I assume "solve for x a...OK, I'll try it. I assume "solve for x as a function of y" means "massage the equation until you have x on one side of the eqn, with only ys on the other side."<br /><br />We start here:<br /><br />y = x/(x-1)<br /><br />Multiply both sides by (x-1):<br /><br />y(x-1) = x<br /><br />We're not happy yet because we have x on both sides of the eqn. We continue by simplifying:<br /><br />xy - y = x<br /><br />Move all x-related stuff to one side:<br /><br />-y = x - xy<br /><br />Rewrite rhs:<br /><br />-y = x(1 - y)<br /><br />Now divide both sides by (1 - y):<br /><br />-y/(1-y) = x<br /><br />et voila!<br /><br />I'm reviewing math previous to teaching dd, so if I did that wrong, please let me know!FedUpMomhttps://www.blogger.com/profile/00951858601020687242noreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-46554972416589695892010-03-14T18:13:51.637-07:002010-03-14T18:13:51.637-07:00This same professor, Cliff Mass, posted this same ...This same professor, Cliff Mass, posted this same problem on youtube about three years ago.<br /><br /><a href="http://www.youtube.com/watch?v=ymvSFunUjx0" rel="nofollow">http://www.youtube.com/watch?v=ymvSFunUjx0</a><br /><br />He is a professor of Atmospheric Science at the University of Washington, and the video asks people to read wheresthemath.com and to reject the NCTM progressive math standards.<br /><br />I'm surprised the "cheaters network" hasn't told more people the answers to his little test (psst: 4b is its own inverse!).rockynoreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-5861496364200780632010-03-14T16:47:02.666-07:002010-03-14T16:47:02.666-07:00They mean solving for x as a function of y, and yo...They mean solving for x as a function of y, and you should read that as y = x/(x-1). This is the kind of fraction that students have fits with, since they want to break up the denominator in creative ways.ChemProfnoreply@blogger.comtag:blogger.com,1999:blog-7691251033406320222.post-85717704343819471362010-03-14T16:11:26.699-07:002010-03-14T16:11:26.699-07:00Shouldn't it be "only 16% could solve for...Shouldn't it be "only 16% could solve for Y"?<br /><br />y=1-1 = 0farmwifetwohttps://www.blogger.com/profile/02680758336779501712noreply@blogger.com