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 06032013, 01:50 AM #1Member
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Solving a quadratic equation using java
Solving a quadratic equation
Write two methods quadraticEquationRoot1 which takes as input 3 doubles, representing a,b,c and returns the larger of the two roots and quadraticEquationRoot 2 which takes as input 3 doubles, representing a,b, and c (in that order) and returns the smaller of the two roots.
Note that if there is a double root (because the square root term is 0), your two methods will return the same thing. Finally note that you may assume that the numbers a,b,c are chosen so that the square root is never the square root of a negative number.
I have the following but I don’t know to the write the second method and how to add a “return”.
I have below the first method. I am not sure how to write the second method.
I am not allowed to use Scanner or have print statements *
double quadraticEquationRoot1(int a, int b, int c)
{
if(Math.sqrt(Math.pow(b, 2)  4*a*c) == 0)
{
return b/(2*a);
}else
{
int root1, root2;
root1 = (b + Math.sqrt(Math.pow(b, 2)  4*a*c)) / (2*a);
root2 = (b  Math.sqrt(Math.pow(b, 2)  4*a*c)) / (2*a);
return Math.max(root1, root2);
}
}
 06032013, 02:57 AM #2Moderator
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Re: Solving a quadratic equation using java
The second method could use Math.min(), I suppose. (Once you have them doing what you want you might consider seeing if they can be simplified)
What do you mean by "add a return"? The code you posted has return statements.
 06032013, 03:51 AM #3Moderator
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Re: Solving a quadratic equation using java
Cross posted at Create a java program to solve quadratic eqations
 06032013, 04:58 AM #4Senior Member
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Re: Solving a quadratic equation using java
Due to limitations of floating point math in software you may want to check out Quadratic equation  Wikipedia, the free encyclopedia
Regards,
JimThe Java^{TM} Tutorials  SSCCE  Java Naming Conventions
Poor planning on your part does not constitute an emergency on my part
 06032013, 10:05 AM #5
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Re: Solving a quadratic equation using java
cenosillicaphobia: the fear for an empty beer glass
 06032013, 01:46 PM #6Senior Member
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Re: Solving a quadratic equation using java
It was because of your post within the last few months that I remembered it. I couldn't find the post in which you stated the same thing so I just repeated it and provided a reference.
Regards,
JimThe Java^{TM} Tutorials  SSCCE  Java Naming Conventions
Poor planning on your part does not constitute an emergency on my part
 06032013, 04:20 PM #7
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Re: Solving a quadratic equation using java
I you're interested in this stuff. google for "Jenkins Traub"; that algorithm numerically finds all roots of any polynomial, smallest to largest and is numerically very stable. There exists a faster version of this algorithm for real values only (the general case finds complex roots).
kind regards,
Joscenosillicaphobia: the fear for an empty beer glass
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