What is the mistake in logic?

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Given the values of x real and n natural positive, calculate:

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#include <stdio.h>

int main(){

    float x = 0.0;
    int n = 0;
    int soma = 0;
    int fat = 1;

    printf("Digite um valor:");
    scanf("%f", &x);
    printf("Digite a quantidade de operações:");
    scanf("%d", &n);

    for(int i = 1; i <= n; i++){
        soma = (x + i)/fat;
        fat = fat * i;
}
    printf("A soma n pra S = x+n/n!\nÉ: %d", soma);
    return 0;
}
c algorithm logic

  • Question: does the sum have only 4 terms even or should all terms between 3 and n be summed as well? The way you’ve posted jumps from 3 to n.

  • 1

    And it shouldn’t be soma += (x + i)/fat? The way you override the value with each iteration.

  • The sum of the terms starts from 1 to n which is the number of terms chosen for example 5, went to 3 to show how it would be from the beginning of the calculation

  • Anderson applied the attribution operator by addition that was missing, but still continues with a wrong result

  • 1

    Marvin, are you sure soma will always be an integer?

  • I already changed the type to accept floats values, thank you!

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2 answers

1

Three things:

  1. You overwrite the value of soma every iteration of the loop;
  2. You define soma as a whole;
  3. You must first multiply the fat, then add up;

To correct (1), you will need to change soma = for soma +=. Already to fix the (2) just set soma as float. Item (3) needs to be done because otherwise you will have 2 times the denominator equal to 1. fat starts at 1, generating the term (x+1)/1! , then it is multiplied by i which is also 1, generating in the next iteration (x+2)/1!. In the next iteration it would be (x+3)/2! , etc. That is, the result would be different than expected.

#include <stdio.h>

int main(){

    float x = 0.0;
    int n = 0;
    float soma = 0;
    int fat = 1;

    printf("Digite um valor:");
    scanf("%f", &x);
    printf("Digite a quantidade de operações:");
    scanf("%d", &n);

    for(int i = 1; i <= n; i++){
        fat = fat * i;
        soma += (x + i)/fat;
    }

    printf("A soma n pra S = x+n/n!\nÉ: %f", soma);
    return 0;
}

  • In vdd the fat already starts with 1, so it would be necessary to just put signal assignment for addition in fat also.

  • But putting fat += after the sum the result is the same, it only includes the other fat previously calculated

0

Well, there’s my answer, the result is as expected

#include <stdio.h>
int main(){

    float x = 0.0;
    int n = 0;
    float soma = 0;
    int fat = 1;

    printf("Digite um valor:");
    scanf("%f", &x);
    printf("Digite a quantidade de operações:");
    scanf("%d", &n);

    for(int i = 1; i <= n; i++){

        soma +=(x + i)/fat;
        fat += fat * i;
    }

     printf("A soma de %.2f como x pra S = x+n/n!\nÉ: %.2f",x, soma);
return 0;
}

  • Friend the %.2f round the value up, just take it out and you’ll see the unwrapped result

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