Thread: Problem with formula

Hello, I have a maths assignment and i would like some help putting these formula in code, and how I would implement these in a loop function. The x is given.

An = (-x/n)*An-1 - 1/n*(n-1) * An-2

if x = 3

A(0) = 2
A(1) =0

A(2) = (-3/2)*0 - 1/2*(1)* 0 = -1

This is basically the results for the first 3, I need a loop to continuously do this for any number put for x

Any suggestions ?

You need to retain the last two values (at least).
The first two values are 2 and 0 (apparently).
So initialize a couple of variables with those values and print them:

Code:

    double a = 2, b = 0;
    printf("% f\n% f\n", a, b);

Then start your loop at 2, calculate the new value, print it, and then shift the two saved values over:

Code:

    for (int n = 2; n < 100; n++) {
        double c = -x / n * b - 1.0 / n * (n - 1) * a;
        printf("% f\n", c);
        a = b;
        b = c;
    }

Alternatively, you could store all calculated values in an array.

Code:

    double a[100] = {2, 0};
    for (int n = 2; n < 100; n++)
        a[n] = -x / n * a[n-1] - 1.0 / n * (n - 1) * a[n-2];
    for (int n = 0; n < 100; n++)
        printf("% f\n", a[n]);