sum of squares of two numbers c program

i’m supposed to write a formula for the sum of squares using the given function and its parameters (i am allowed to add variables) but i can’t seem to get it right. the formula i came up with only computes the summation of the two numbers (not squared). please help, thank you!

/* Suppose nLowerBound is -2 and nUpperBound is 4.
    The function computes:
    (-2)^2 + (-1)^2 + (0)^2 + (1)^2 + (2)^2 + (3)^2 + (4)^2 = 35
    The function returns 35.
*/

int sumOfSquares(int nLowerBound,
                 int nUpperBound) {
    // your code here
    int nSum;
    nSum = ( (nUpperBound * (nUpperBound + 1)) - (nLowerBound * (nLowerBound - 1)) ) / 2;
    
    return nSum;

>Solution :

The simplest way to compute the sum is to use a loop:

int sumOfSquares(int nLowerBound,
                 int nUpperBound) {
    // Initially set the sum as zero
    int nSum = 0; 

    for (int i=nLowerBound; i<=nUpperBound; i++) {
        // for each number between the bounds, add its square to the sum
        nSum = nSum + i*i; 
    }
    
    return nSum;
}