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Homework Help: Calculate the real roots of a quadratic equation

  1. Apr 10, 2006 #1
    Please Help!

    I designed this "PROGRAM"!!! TO calculate the real roots of a quadratic equation....

    but the compiler miracle C kept saying there's something wrong around the "if" word.... saying "unrecognised types in comparison"
    it seem SO FINE to me.... what is wrong?!?!?!?!?!:eek:

    #include <stdio.h>
    #include <math.h>

    int main(void)
    {
    /* Declare variables. */
    double a,b,c,d,e,f;

    printf("This program computes the real roots of a quadratic equations.\n");
    printf("(recall that the general form of quadratic equation is ax^2+bx+c where a, b and c are canstants)\n");

    printf("please enter the first coefficient.\n");
    scanf("%f", &a);
    printf("%f\n",a);

    printf("please enter the second coefficient.\n");
    scanf("%f", &b);
    printf("%f\n",b);

    printf("please enter the third coefficient.\n");
    scanf("%f", &c);
    printf("%f\n",c);

    f=(b*b-4*a*c);

    if(f<0)
    printf("roots are not real.\n");

    else
    d=((-1)*b+sqrt(f))/(2*a);
    e=((-1)*b-sqrt(f))/(2*a);
    printf("%f, %f",d,e);

    /* Exit program. */
    return 0;
    }
    /*--------------------------------------------------*/
     
    Last edited: Apr 10, 2006
  2. jcsd
  3. Apr 10, 2006 #2
    1. To read doubles, use %lf in scanf().
    2. You will need braces around the else body.
     
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