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Wednesday, June 28 2017 @ 07:22 AM CDT
 Forum Index >  Test Paper Related >  Primary 6 Matters
 Math(8 Aug 2013)
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By: vivilau1112 (offline)  Saturday, August 17 2013 @ 10:09 AM CDT (Read 1205 times)  
vivilau1112

I posted a question on 8 Aug 2013, regarding speed. I have heard it can also be solved by quadratic, could someone give a simple but clear explanation about how it works?Help is much appreciated Smile

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By: echeewh (offline)  Saturday, August 17 2013 @ 07:13 PM CDT  
echeewh

Hey <vivilau>,

You have not only heard about the quadratic equation (method) but have actually encountered / reviewed it. Big Grin. The worked solution that I provided there makes use of the quadratic form to solve for the speed of Mr Tan, s(T), as shown below:

[s(T) × s(T)] - 20s(T) - 4800 = 0

Hope you find this useful. Thank you.

Do let me know again if there's further clarification.

Cheers,
Edward

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By: vivilau1112 (offline)  Saturday, August 17 2013 @ 10:14 PM CDT  
vivilau1112

Oh, in the question, I meant that how to use the quadratic formula in the calculator, and the basic understanding of the formula. Oops!

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By: echeewh (offline)  Sunday, August 18 2013 @ 03:10 AM CDT  
echeewh

Hey <vivilau1112>,

With reference to my worked solution, the quadratic eqn* is :

(s x s) - 20s - 4800 = 0

I think most Primary school recommended calculators do not have this built-in function as in other higher models** (meant for higher levels). Frankly I did not use calculator to do this. And at your level, use your understanding of Factorization to resolve this.

In this case, think of all possible factors of 4800 and the 2 factors that will give you a difference of 20. Here, the 2 possible factors are 60, 80.

And, -80 + 60 = -20 ...

Factorizing the above quadratic eqn,

(s + 60)(s - 80) = 0

s = -60, 80


* Quadratic eqn is taught in Sec school.
**Do check with the respective user guide that comes with your calculator to see if there is a built-in function for quadratic eqn, where I think it will require you to input certain values for the formula.

=========

Hope this helps.

Cheers,
Edward

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By: echeewh (offline)  Sunday, August 25 2013 @ 06:02 PM CDT  
echeewh

Hey <vivilau1112>,

If you really need to make use of the Quad eqn / function in your calculator (provided its already built-in), press <Mode> to see if there is an <Eqn> option. Press that option and look for <Quad> or an eqn with { ax2 + bx + c } where 2 is the squared of x.

Hope you find this useful.

Cheers,
Edward.

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