Its a long time ago since I did quadratic equations but if my memory serves me right the solution is
b= (-1 +/- (1+0.6a)^1/2)/0.3
Is there someone who could help me re-arrange this Formula please?
The Formula is
a = 0.15 * b * b + b
I need to calculate "b" in terms of "a" so I can place the Formula into a cell in Excel Program.
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Its a long time ago since I did quadratic equations but if my memory serves me right the solution is
b= (-1 +/- (1+0.6a)^1/2)/0.3
a = 0.15b * b + b
a = 0.15b2 + b
a = b + 0.15b2
a + -1b + -0.15b2 = b + -1b + 0.15b2 + -0.15b2
b + -1b = 0
a + -1b + -0.15b2 = 0 + 0.15b2 + -0.15b2
a + -1b + -0.15b2 = 0.15b2 + -0.15b2
0.15b2 + -0.15b2 = 0.00
a + -1b + -0.15b2 = 0.00
Now I'm confused!
In my Formula , I substituted 1.5 for b , and that gives a = 1.8375
Therefore, if I substitute 1.8375 for a in your Formula Verad, then b should come up as 1.5
0.6 * 1.8375 = 1.1025
1 + 1.1025 = 2.1025
2.1025^1/2 = 1.45
-1 + 1.45 = .45
.45/.3 = 1.5
Thank You very much Verad.
And thank you for your efforts as well IntelliGeorge.
I don't suppose you could explain how you got the Formula Verad, in a similar way as how Intelligeorge tried to show?
Not important as I have what I needed, but am curious, and Giving the Method is much more beneficial to the pupil than giving only the amswer.
If you are busy I completely understand and very much appreciate what you have given regardless.
Last edited by moeee; 11-04-08 at 07:47 PM. Reason: Added a Question
so how do you get " +/- " into a spreadsheet? Don't work on mine ? Using two columns for the formula ,one with + and the other with - I get different results, strange ? a with + b a with - (-1 + (1+0.6* B4)^1/2)/0.3 (-1 - (1+0.6* B4)^1/2)/0.3 4.33333 16.00000 -21.00000 8.33333 10.00000 -21.00000 9.33333 11.00000 -21.00000 369.33333 371.00000 -21.00000 -0.16667 1.50000 -21.00000 0.17083 1.83750 -21.00000 -1.66667 0 -21.00000 -1.66667 0 -21.00000
I gave up tryying to format this , its a joke
Last edited by tytower; 13-04-08 at 11:11 AM.
Probably won't work on mine either, but thats not what I put in mine.
I just used the PLUS.
It works fine and gives the correct answer.
If instead I use the Minus, the answer comes out wrong.
Verad was going a little on memory and perhaps his memory was almost perfect except for this little bit.
I'm happy...and very grateful.
the formula verad gave is used to solve quadratic equations, ie your equation - of the form
y = ax^2 + bx + c ------or in your case-------- a = 0.15b^2 + b
I have attached a graph of your equation here:
the roots of the equation are where the line crosses the horizontal axis - what you are looking for is the same thing essentially, just shifted up above / below the horizontal axis depending upon your value of a
so, the +/- is supposed to be there, its just that it is not always a useful solution
Quadratic equations have two solutions so the + and - is supposed to be there.
To go through the derivation of the solution is a bit complicated but if you do a google search on solution to quadratic equation the 4th item explains it.
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