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02 Jun 12
20:01
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16 Sep 06
Hi, I have an equation in my study book which goes as follows:
1. 8 = x + 1.2(7-x)
2. 8 = x + 8.4 - 1.2x
3. 0.2x = 0.4
4. x = 2
Can anyone tell me how on earth they get from stage 2 to stage 3?
Many thanks
1. 8 = x + 1.2(7-x)
2. 8 = x + 8.4 - 1.2x
3. 0.2x = 0.4
4. x = 2
Can anyone tell me how on earth they get from stage 2 to stage 3?
Many thanks
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Move the x's from the right to the left and change the + to a - and the - to a + and move the 8 to the right and change it to a minus.
so after stage 2 it becomes... -x + 1.2x = 8.4 - 8 then simple to get to stage 3 from there. |
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Thanks, that was a very quick reply. I still don't really get it - I probably need to study equations.
Thanks very much |
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When you move something from one side of the equation to the other you swap the +/- over.
so if 5 = x + 2 then 5 - 2 = x or -x = -5 + 2 Anyway you may not need to study equations, if you go online and type in something like "equation solver" then there are sites which can do if for you. Good luck. |
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Many thanks for your help. I do need to study them as it's for an exam, and they seem to assume you can do equations already - I've been looking them up and it's actually pretty easy I think I'm getting there.
Thanks again - I wish I'd paid attention at school. |
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another way of looking at it - if you do the same thing to both sides you're not changing the equation :
8 = x + 8.4 - 1.2x 8 - 8.4 = x + 8.4 - 1.2x - 8.4 8.4 - 8.4 = 0 so can be removed from the right -0.4 = x - 1.2x = -0.2x now multiply both sides by -1 |
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The element 1.2(7-x) means
1.2*7 - 1.2*x and 1.2*7=8.4 Can you see it now? |
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Yes, thanks a lot guys. I can remember learning equations at primary school and I didn't understand them then - one of my mates told me an easy way was that if x= yz you just put numbers in so that it becomes 6=3 x 2, then you can switch the numbers round.
That's as far as my equations education ever went and I've somehow stumbled through a few exams involving them recently (and passed!) Having now had a look online I can see now how to do fairly simple equations and what the principles are, which is all I need to know. Thanks a lot for your help - some very helpful people on here |