Array of Coefficients and function fragments help!!

[Totes my goat]

Hey Y'all I have this problem that I am having trouble with:

Write a function which takes an array of coefficients, ai and and integer n, and returns the value of the following equation. Also write a code fragment to show how to call your function.
y=a0 + a1(x) + a2(x^2) + a3(x^3) + .... an(x^n)

Heres what I have so far:

int equation(int a[i], int n); //function declaration
...
equation(a[i], n); //call function
...
int equation(int a[i], int n)  //function prototype
{

Any help/suggestions is greatly appreciated. Thanks!