Methodology for Solving for a Variable

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mikexz

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Feb 21, 2006
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I am currently in gr12 physics and I am finding that I am VERY slow at solving for a variable (like 20min compare to other students 3 min) when given multiple equations (so need to substitute many times). I usually end up trying every possible combination of substituting equations before I finally solve for the variable. IS there a certain methodology I should use? I am usually lost when I am asked to solve for a variable. How can I get faster (I think the problem goes beyond just practice)?

thanks
 
I'm not trying to be cute. But, it sounds to me like you need to review your Algebra.
I get the idea that you may run across a formula like s=4gt^3 and you want to solve "explicitly" for say, t. If that's what you are after, then you do need to review Algebra. If it is something else, you will have to be more explicit in your question.
 
Can you give us an example problem?

Can't see how we can help otherwise....
 
I am currently in gr12 physics and I am finding that I am VERY slow at solving for a variable (like 20min compare to other students 3 min) when given multiple equations (so need to substitute many times). I usually end up trying every possible combination of substituting equations before I finally solve for the variable. IS there a certain methodology I should use? I am usually lost when I am asked to solve for a variable. How can I get faster (I think the problem goes beyond just practice)?
Click to expand...

Hello, mikexz,

It sounds like you’re trying to solve a system of linear equations, with two or more variables. I would suggest various possible approaches. I can’t “teach" them to you online, but can send you looking for info:

1) If you have two equations with two unknowns, use the “substitution” or “elimination” methods.

2) For three or four equations and unknowns, use the Gaussian elimination method.

http://www.sosmath.com/matrix/system1/system1.html
http://ceee.rice.edu/Books/CS/chapter2/linear43.html

3) For three or more equations and unknowns, solve using matrices on your calculator. (You can do matrices by hand, but the calculator handles this very readily – a very powerful tool).
 
thanks :D

I was solving for a variable using 3-6 equations (usually trying to make proofs). I think matrices should solve my problem, I am going to try to self teach it for now.

thanks again.
 
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