
By: vivilau1112 (offline) Saturday, August 17 2013 @ 10:09 AM CDT (Read 1225 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

Junior
Registered: 04/13/11 Posts: 16





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. . 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

Active Member
Registered: 04/21/11 Posts: 627





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.

Junior
Registered: 04/13/11 Posts: 16





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 builtin 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 builtin function for quadratic eqn, where I think it will require you to input certain values for the formula.
=========
Hope this helps.
Cheers,
Edward

Active Member
Registered: 04/21/11 Posts: 627





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 builtin), 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.

Active Member
Registered: 04/21/11 Posts: 627



