Question

Write a C++ prgm to find roots by using quadratic formula?

Answer 1

@ajprincess

Answer 2

sorry i'm not very good at c :(

Answer 3

i think u should try yourself first and then if you face any problem,i will help you.

otherwise i can give you source code but that would not be good for you

Answer 4

JAVA JAVA :P

Answer 5

I will help with C, it works on C++, but if you want in C++, just make some changes (little).
Look, you said quadratic, with Math it's like :
\[Ax^{2} + Bx + C\]
Where A,B and C are constants.
So we need the following variables : A, B, C to represent the constant, and another variable for the DELTA, we called it D, and another two variables for the solutions, X1,X2.
Lets start :
#include<stdio.h>
#include<stdlib.h>
#include<math.h> // so we can use the function sqrt().
// We declare our variables here;
int A = 0,B = 0,C = 0, D;
float X1 = 0,X2 = 0;
// We will make a function to calculate Delta.

int Delta (int a, int b, int c){
D = B*B - (4 * A * C);
return D;
}
// Now our main program
int main(){
printf("Enter the value of A : "); //The user will enter the value of A,B and C.
scanf("%d", &A);
printf("Enter the value of B : ");
scanf("%d", &B);
printf("Enter the value of C : ");
scanf("%d", &C);
D = Delta(A,B,C);
if (D<0) {
printf("There is no solution\n"); //In case Delta is inferior than 0.
}else if (D == 0) {
X1 = -B/(2*A);
printf("There is one solution : X = %f\n", X1);
}else { // Delta > 0
X1 = (-B + Sqrt(D))/2*A; //Calculate X1, and X2
X2 = (-B - Sqrt(D))/2*A;
printf("There are two solutions : X1 = %f and X2 = %f\n", X1,X2);
}
system("pause");
}

Hope that's help you.
Good luck.

Answer 6

@ktobah
may be you missed brackets around 2*A in the case with Delta >0 : (2*A)

Answer 7

No @nick67 , it's ok there because I already putted (-B + Sqrt(D)) between brackets.

Answer 8

@ktobah
sorry ktobah, but the way you wrote the expression works this way:
\[\left( -B+\sqrt{D} \right)/2*A\]that is, the content of brackets is first divided by 2, then the partial result is multiplied by A; we instead would like that the content in brackets should divided by the product 2*A \[(-B+\sqrt{D})/(2*A)\]:-)

Answer 9

Ah yeah true, good remark, thanks.
May the asked change this in his program.

Answer 10

you're welcome

Answer 11

@Yahoo! http://www.cplusplus.com/forum/general/36313/

Answer 12

All i can say is try to enumerate how would someone will solve it like a trial and error first.
This trial and error is equivalent to if else statements. Under it should be the process of each way to solve it.
Hope that helped someone.
xD