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Thread: Kwadratic formula
 03262012, 12:19 PM #1Member
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Kwadratic formula
Hi Im quite new to java and programming in general and I was hoping on getting some help with this piece of code.
class kwadratic {
public static void main(String []args){
for (double xxx=1000; xxx<1000;xxx++){
double equation = xxx*xxx*38*xxx+4;
}
if (equation ==0){
System.out.println(xxx);
}
}
}
Im using Netbeans ...if it matters.
 03262012, 12:24 PM #2
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Re: Kwadratic formula
That way you'll only find one root (2.0) if you're lucky; the other root (2/3) can not be found that way. Why don't you apply the close form formula (b+sqrt(b*b4*a*c))/(2*a).
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
 03262012, 12:38 PM #3Member
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Re: Kwadratic formula
Well I wanted to find the solution without the formula to make it as basic as possible.
 03262012, 12:41 PM #4Member
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Re: Kwadratic formula
Is there any way of letting the xxx increment by ..lets say 0.01 instead of 1 ?
 03262012, 12:55 PM #5
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Re: Kwadratic formula
Sure, add 0.01 to variable xxx each time through the loop:
Java Code:for (double xxx= 1000; x < 1000; x+= 0.01) // ...
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
 03262012, 12:59 PM #6Member
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 03262012, 01:25 PM #7
Re: Kwadratic formula
hi,
a variable cannot be accessed outside a block
also, every instance of the variable "equation" should be checked, but u're checking it only once after the end of the loop
regards
dhilip
 03262012, 01:32 PM #8Member
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Re: Kwadratic formula
Uhm , in nooblanguage please. Or most preferably in code form ???
 03262012, 01:34 PM #9
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 03262012, 01:39 PM #10Member
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 03262012, 01:51 PM #11
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Re: Kwadratic formula
So you're happy with this? Your program only finds solutions to your quadratic formula if the root is 1000+i*0.01. An ordinary quadratic formula isn't too difficult to implement ... it's not like a JenkinsTraub method that works on arbitrary polynomials ...
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
 03262012, 02:27 PM #12
Re: Kwadratic formula
Hi,
adding "0.01" to "double xxx=0" gives us approximate double values, not exact increment
for example,
Java Code:for(int xxx=0;xxx<1;xxx+=0.01) { System.out.println(xxx); }
(first 15 output values..)
Java Code:0.0 0.01 0.02 0.03 0.04 0.05 0.060000000000000005 //this is nonexact 0.07 0.08 0.09 0.09999999999999999//nonexact 0.10999999999999999//nonexact 0.11999999999999998//nonexact 0.12999999999999998//nonexact 0.13999999999999999//nonexact
hence even "2.0" may not be displayed
I learnt it at Java theory and practice: Where's your point?
regards
dhilipLast edited by noobplus; 03262012 at 06:13 PM.
 03262012, 02:32 PM #13
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Re: Kwadratic formula
Of course you haven't read my original reply:
Originally Posted by JosAH
JosBuild a wall around Donald Trump; I'll pay for it.
 03262012, 02:37 PM #14
Re: Kwadratic formula
 03262012, 03:32 PM #15
Re: Kwadratic formula
Java Code:/** *@author:dhilipkumar(noobplus) */ public class kwadratic { static double equation; static double incrementedvalue; static double repeatchecker=1; public static void main(String []args){ for(int x=0;x<11;x++) { for(int i=1;i<11;i++) { for(int j=0;j<10;j++) { if(j<i) { incrementedvalue=(x+(double)j/(double)i); equation = (incrementedvalue*incrementedvalue*3)(8*incrementedvalue)+4; if ((equation==0) && (incrementedvalue!=repeatchecker)) { System.out.println(incrementedvalue); repeatchecker=incrementedvalue; } } } } } } }
Java Code:0.6666666666666666 2.0
regards
dhilipLast edited by noobplus; 03262012 at 03:40 PM.
 03262012, 03:33 PM #16
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 03262012, 03:36 PM #17
Re: Kwadratic formula
 03262012, 04:11 PM #18
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 03262012, 04:17 PM #19
Re: Kwadratic formula
"Kwadratic" is my new favorite word.
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 03262012, 04:20 PM #20
Re: Kwadratic formula
Last edited by noobplus; 03262012 at 04:26 PM.
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