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Help explain how to write algorithm

Am interested in IT but am not a computer scientist, am only teaching my self. Please i have a problem with algorithm, can you give me tips on how to go about it. here is th problem am trying to solve:
A quadratic equation can be written in the form, Ax2+Bx+C=0. Develop an algorithm and draw a flowchart to read the coefficients of A, B, and C. Calculate the roots and print out.

tressureme

Newbie Poster

3 posts since Aug 2007

Reputation Points: 10

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4 Years Ago

This is a source code example to calculate that expression with any value, you can test it at http://agec.ath.cx/eq , two functions to calculate each ± result, and one condition to put the two values (the real one and the imaginary) in the imaginary case (b < 4ac), tomorrow I'll inspect the code for errors and I'll add the graph.

<?php

/**
 * @author Martin Caminoa
 * @license MIT
 */

function eq_plus($a, $b, $c){
	$value=array();

	if ($b < (4*a*c)){

		$value[0] = (-1*-$b) / (2*$a);
		$value[1] = ((sqr($b + (4*$a*$c))) / (2*$a));
	}
	else
	{
		$value[0] = ((-$b + sqr($b - (4*$a*$c))) / (2*$a));
	}

	
	return $value;
}

function eq_minus($a, $b, $c){
	$value=array();

	if ($b < (4*a*c)){

		$value[0] = ((-1*-$b) / (2*$a));
		$value[1] = ((sqr($b - (4*$a*$c))) / (2*$a));
	}
	else
	{
		$value[0] = ((-$b - sqr($b - (4*$a*$c))) / (2*$a));
	}
	
	return $value;
}

// get the square of a number
function sqr($value, $power = 2){      // $power = 2 default value
	
    for($i = 1; $i < $power; $i++){
		$value = $value * $value;
	}
	return $value;
}

$a=$_GET['a'];
$b=$_GET['b'];
$c=$_GET['c'];

// display results
if($b < (4*a*c)){
	echo "Results in imaginary numbers";
	$result = eq_plus($a,$b,$c);
	echo "+ = ". number_format($result[0], 2);
	echo " i". number_format($result[1], 2) ."";
	$result = eq_minus($a,$b,$c);
	echo "- = ". number_format($result[0], 2);
	echo " i". number_format($result[1], 2) ."";
}

if($b > (4*a*c)){
	echo "Results in real numbers";
	$result = eq_plus($a, $b, $c);
	echo "+ = ". number_format($result[0], 2) ."";
	$result = eq_minus($a, $b, $c);
	echo "- = ". number_format($result[0], 2) ."";
	
}

// show input form 
$form = "<form action=\"index.php\" method=\"GET\">";
$form .= "a <input type=\"text\" name=\"a\" />&nbsp;";
$form .= "b <input type=\"text\" name=\"b\" />&nbsp;";
$form .= "c <input type=\"text\" name=\"c\" />";
$form .= "<input type=\"submit\" /></form>";

echo $form;

?>

martin5211

Posting Whiz in Training

271 posts since Aug 2007

Reputation Points: 52

Solved Threads: 23

4 Years Ago

Yeah the only real problem is with complex numbers.

iamthwee

Posting Expert

5,950 posts since Aug 2005

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4 Years Ago

Thanks for your help but i just got started and cant really understand all those jargons. I've not really entered into programming am still an introduction on how to write algorithm not program. if you don't mind please use simply language, i can draw the chart but i don't understand algorithm.

tressureme

Newbie Poster

3 posts since Aug 2007

Reputation Points: 10

Solved Threads: 0

4 Years Ago

Pseudo language reminds me to learn another language :) The code have some errors, like the absence of the square root and another condition to put: (sqr(b) - (4ac)) have negative value (nan if I do the square root). Basically, there three functions, one to calculate the square because I haven't a built-in function in PHP to do this, and two functions with the same resemblance to calculate with the quadratic formula ((-b ± sqrt( sqr(b) - (4ac) )) / (2a)).

I use parenthesis to make the order of precedence of the operations and yes, the logic will be more complex dealing with complex numbers.
Each function return the values in a array. An array is a container of data. So, in this way, I can save the two terms of the imaginary result and display then.

The part below the functions there are to display the results. First, to get the parameters sended by the form and store in variables. Then, execute the functions with the parameters obtained. Now then, a condition to show imaginary or real results and finally, the form to input the data. I'm assigning strings to a variable and concatening another strings, then I show the variable with all strings using HTML code.

I have enclosed the new source code, maybe it is more clear.

Attachments index.php (2.13KB)

martin5211

Posting Whiz in Training

271 posts since Aug 2007

Reputation Points: 52

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4 Years Ago

This is the last corrected version, tested the results with Mathematica from Wolfram Research.

Attachments index.php (2.36KB)

martin5211

Posting Whiz in Training

271 posts since Aug 2007

Reputation Points: 52

Solved Threads: 23

4 Years Ago

This is the last corrected version, tested the results with Mathematica from Wolfram Research. The first version is like unkempt - very ugly.

First, if you have to deal with an algorithm, build one, you will have to separate the business logic (like functions to do math operations in this occasion) from the user interface. We have two problems. I recommend start with the business logic always.

We use variables or arrays to contain the values. Both are the same, array can be defined as a variable conjunct, each one with an index to make more easy the location. I'm using the symbol equal to assign the result of the operation (with variables) to unique array index, separating the terms.

Given the parameters by the function, I use conditions to define an action in accordance with an event. In this case, we know that I can't apply the same formula with any given value.

In the square function of a number, I'm using a controlled loop to make a repetitive task of multiply a parameter by itself given the number of times by another parameter too (in this case, parameter can be omitted, have a default value, two times).

I don't know how to put simpler, but in almost every language you can do math operations easily like with a calculator. The problem growth when you don't have built-in functions in the language to make operations, you have the possibility to use more specialized libraries and collection of objects from third-party sometimes. But if it doesn't exist you will need to create one using only the existent functions like these.

Display the result is easier, you will have to put format to the given data, like carriage returns (or line feed). I'm assigning the array results and format properties to a variable and then I use the echo function to display the variable content.

I hope that you have a better vision of an algorithm. I do not use a simple language in my life, I think in minimal or by part, then I apply the interpretation directly using the final language.

martin5211

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271 posts since Aug 2007

Reputation Points: 52

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4 Years Ago

Hi- can anybody help
Write an algorithm using a procedure called quadratic for a program that solve a quadratic equation of the form ax(2) + bx + c = 0

Thx
Jessika

gjessika

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2 posts since Jan 2007

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4 Years Ago

An array called MARK stores the marks of 20 pupils in mathematics.
(i) Write an algorithm that uses a while loop to input marks of 20 pupils, in the array.
(ii) Assuming that no two pupils are allocated equal marks, search the array for a mark of
50 and print it.
(iii)Modify a mark of 65 from the array, so that the new mark is 75.

gjessika

Newbie Poster

2 posts since Jan 2007

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1 Year Ago

i am just in the 10th grade. i have no idea of what is written on this page. please let's start from basics. thank you for trying.

science994

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1 post since Aug 2010

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1 Year Ago

Show Comments

It seems like this topic has veered way off.

#1: What is an algorithm?[INDENT]An 'algorithm' is an effective method for solving a problem expressed as a finite sequence of instructions

( http://en.wikipedia.org/wiki/Algorithm )
An algorithm can be expressed by: natural language (see example below), flow charts, psuedocode, control tables, etcetera.[/INDENT]
#2 How do I go about writing an algorithm?[INDENT]Let's go about writing a basic algorithm for the problem you wrote:
A quadratic equation can be written in the form, Ax2+Bx+C=0. Develop an algorithm and draw a flowchart to read the coefficients of A, B, and C. Calculate the roots and print out.** You should have an understanding of the quadratic equation before beginning this.

Okay, first lets start by listing the inputs and outputs we need to solve our problem.

Wait!!!! What is an input and an output!?
Well, an input is information we need to gather in order to process our problem, this is information supplied by the person who wants you to solve their problem, for the purpose of this problem our inputs will be the A, B, and C coefficients. An output is the information that we give back to the person as we process the problem. For this problem our outputs will be the two roots.
Quadratic Equation Algorithm (Natural Language: English)
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