Write a method called PiApproximation that receives one integer parameter and it returns one value. The method approximates the value of pi by summing all the terms of this series: 4/1 - 4/3 + 4/5 - 4/7+ 4/9 - 4/11+ ...
The method accepts one parameter which represents the number of terms to sum and then it returns the sum of the first n terms of this series.