September 24th, 2008, 02:45 PM  #1 
Newbie Joined: Sep 2008 Posts: 5 Thanks: 0  Isolating y
I am currently doing an assignment in an applications of mathmatic 11's class and am having alot of trouble with isolating variables, and I would really appreciate some help. I finished most of the assignment but the last question has me stumped. (x/3) + (2x/5) = (17/5y) + (4/10) It seems like each question I do, is an entirely different scenario that for some reason I can't wrap my head around. Any help would be greatly appreciated. 
September 24th, 2008, 04:44 PM  #2 
Senior Member Joined: Jul 2008 Posts: 895 Thanks: 0  Re: Isolating y
This is not an easy topic for a lot of people when they first encounter it. In this question you can first simplify the numerical fraction 4/10. Move that to the left ...[added on the right, so subtracted on the left.] This isolates the term containing "y". Note that if A = B, then B = A, so you can write 17/5y = whatever you now have on the left. Now, you have three fractions on th right, none of which contain y. Make them into one fraction using the rules of arithmetic. Now you have 17/5y = C/D That is, a fraction on the right. Now invert both [If A/B = C/D then B/A = D/C] Multiply by 17 and divide by 5 to isolate y on the left. Do the same to the right, of course. Now you should be just about done. NOTE: I have pointed out two methodologies here. One is "Do the same to both sides", the other is "Transposing", or "Move and use the opposite operation". This takes LOT of practice with minor problems before moving into more complicated problems. Your problem is common ...not enough practice exercises built slowly from the very simple to the more complex. The main thing is to collect like terms. If there is only one term containing the sought variable, then you need to isolate the rest, which is what is being done here. The teacher is between a rock and a hard place with this sort of skill learning. Not too much exercise means not enough learning to make it easy. More exercise and the complaint is that it's boring. If you want some day to play Chopin, you have to practice your scales ...every day. Look for other sources in used book stores. 

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