help need proper equation!

For this program I have to obtain the variance. The variance is obtained by subtracting the calcAverage from each value in testvals, squaring the values obtained, adding them, and dividing by the number of elements in testvals. Basically the last line of code I need help because I can't figure out how to do all the math with one formula. This is the formula I need help with:

Code:

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variance = ((testvals[i] - (testvals, MAXELS)));

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I know thats not right obviously. So any help would be greatly appreciated :)
Heres what I have so far:

Code:

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#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;
 
  const int MAXELS=14;
  float calcAverage(int [MAXELS]); //function prototype
  float variance(int [MAXELS]); //function prototype
int main()
{
  int testvals[MAXELS] = {89, 95, 72, 83, 99, 54, 86, 75, 92, 73, 79, 75, 82, 73};
  cout << "The average of these numbers is: " <<calcAverage(testvals) <<endl;
  cout << "The variance of these number is: " <<variance(testvals) <<endl;
system("pause");
  return 0;
}
//find the average value
float calcAverage(int testvals[MAXELS])
{
    int i;
    float calcAverage, total=0;
    for(i=0; i < MAXELS; i++)
  {
    total=total+testvals[i];
  }
    calcAverage=total/MAXELS;
      return calcAverage;
}

//find the variance
float variance(int testvals[MAXELS])
{
      int i;
      float calcAverage, sqd, variance=0;
      for (i=0; i < MAXELS; i++)
  { 
      variance = ((testvals[i] - (testvals, MAXELS)));
  }
  return variance;
}

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Please help me out! I would really appreciate it

Quote:

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I can't figure out how to do all the math with one formula

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Is doing the calculation in multiple steps not an option?

Actually it is an option but I just don't know how to do it at all.