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**Object: I.
To write a program to calculate roots of a quadratic equation ie ax ^{2}+bx+c=0.**

Download this full program | Lab 4 | in pdf format

**
Background Theory:**

Like most languages C uses keywords to implement the decision control instruction. The general form of if statement looks like:

if (this condition is true)

execute this statement;

The keyword tells the compiler that what follows, is a decision control instruction. The condition following the key word if is always enclosed in parentheses. If the condition, whatever it is, is true, then the statement is executed. If the statement is not true the statement is not executed; instead the program skips past it.

__
The ____
if____ statement__

The if statement has the same function as other languages. It has three basic forms, among which given sort is used to execute the given object.

if (expression)

statement_{1}

else if (expression)

statement_{2}

else

statement_{3}

**
Object
Theory:**

First step to write the object is to find what lies inside the quadratic equation ie ax2+bx+c=0. It has two roots &, depending upon the nature of determinant √d=√(b2-4ac) there may exist three sorts of root pair as given:

I.
√(b^{2}-4ac)>0
:
Real
and unequal

II.
√(b^{2}-4ac)=0
:
Real
and equal

III.
√(b^{2}-4ac)<0
:
Imaginary and conjugate

Also
it should be noted that real roots are equal and imaginary roots in case three
defer only in sign to say (x_{2})_{
imaginary}
= (x_{1})_{imaginary}.

**
Code:**

//
Program to calculate roots of a quadratic equation ie ax^{2}+bx+c=0 //

# include <stdio.h>

# include <conio.h>

#include <math.h>

void main()

{

float a, b, c, d, x1,x2;

clrscr();

printf("Enter coefficients of quadratic equation ie a, b and c: ");

scanf("%f%f%f", &a, &b, &c);

d=b*b-4*a*c;

if (d>0)

{

x1= (-b+(sqrt(d)))/(2*a);

x2= (-b-(sqrt(d)))/(2*a);

printf("Roots x1= %f and x2= %f are real and unequal", x1, x2);

}

else if (d==0)

{

x1= (-b/2*a);

x2= x1;

printf("Roots x1= %f and x2= %f are real and equal", x1, x2);

}

else

{

x1= (-b/2*a);

x2= sqrt(abs(d))/(2*a);

printf("Real part= %f and imaginary part= %f are complex conjugates", x1,x2);

}

printf(“\n\n\t\t Press any key to continue…”);

getch();

}

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