how to make a function that would calculate the sum of the five terms of an arithmetic progression?-CodePudding

how to make a function that would calculate the sum of the five terms of an arithmetic progression, but the parameters of the function – the initial term and the difference – are entered by the user. I tried this but i have no idea what to do

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
</head>
<body>
<script>
function progress(){
var i, x = 0;
for (i = 1; i <= 5; i  )
{x  = i}
}
</script>
</body>

CodePudding user response：

The following function will work.

function calculate(initialTerm , diff) // 1 , 1
{
  let sum = 0;
  let term = initialTerm;  //1
  for(let i = 0; i < 5; i  )
  {
    sum =term;   //1 3 6 10 15
    term =diff;  // 2 3 4 5  
  }
  console.log(sum);
}

CodePudding user response：

The sum of first n terms in an AP is given by - n/2*[2a (n-1)d] where n is the number of terms, a is initial value and d is the difference.

So you can use the following function -

function progress(a, d) {
     return 5/2*[2*a   4 * d];

}