Thread: quadratic equation

  1. #1
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    quadratic equation

    Hi. the return values are not coming out properly. Any reasons why would be a big help.
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    
    float b;
    float a;
    float c;
    float z;
    
    
    int main()
    {
        printf("please enter a, b and c \n");
        scanf("%f", &a);
        scanf("%f", &b);
        scanf("%f", &c);
    
    
        z= (-b+ sqrt((b*b)-4*a*c))/2*a;
        z= (+b+ sqrt((b*b)-4*a*c))/2*a;
        printf("%f \n");
        printf("%f \n");
    }

  2. #2
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    Missing math.h header. Printf not used properly.

  3. #3
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    Ok I put the header in and changed the printf but still doesn't work.

  4. #4
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    Oops Latest code and what is the input you are giving what is the expected and actual output. Can you provide.

  5. #5
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    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    float b;
    float a;
    float c;
    float z;
    float r;
    int main()
    {
        printf("please enter a, b and c \n");
        scanf("%f", &a);
        scanf("%f", &b);
        scanf("%f", &c);
        z= (-b+ sqrt((b*b)-4*a*c))/2*a;
        r= (+b+ sqrt((b*b)-4*a*c))/2*a;
        printf("%f \n",z);
        printf("%f \n",r);
    }
    quadratic equation-gxe61pu-jpg

  6. #6
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    Make sure that value in sqrt is positive and 2*a should be in brackets.

  7. #7
    C++ Witch laserlight's Avatar
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    Singapore
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    Your implementation of the formula is wrong. For example, this:
    Code:
    z= (-b+ sqrt((b*b)-4*a*c))/2*a;
    should have been:
    Code:
    z = (-b + sqrt(b * b - 4 * a * c)) / (2 * a);
    or if you prefer to use parentheses to be more explicit about the grouping:
    Code:
    z = (-b + sqrt((b * b) - (4 * a * c))) / (2 * a);
    Look very carefully at:
    Code:
    r= (+b+ sqrt((b*b)-4*a*c))/2*a;
    compare closely with the mathematical expression that you are trying to implement.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  8. #8
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    Thank you for the help.

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