added some comments

README.md

@@ -448,12 +448,19 @@ contract Exchange is ERC20 {
         // We are charging a fee of `1%`
         // Input amount with fee = (input amount - (1*(input amount)/100)) = ((input amount)*99)/100
         uint256 inputAmountWithFee = inputAmount * 99;
+
         // Because we need to follow the concept of `XY = K` curve
         // We need to make sure (x + Δx) * (y - Δy) = x * y
-        // So the final formula is Δy = (y * Δx) / (x + Δx)
+        // So the final formula is Δy = (y * Δx) / (x + Δx) = numerator / denominator
         // Δy in our case is `tokens to be received`
-        // Δx = ((input amount)*99)/100, x = inputReserve, y = outputReserve
+        // Δx = ((input amount)*99)/100 = inputAmountWithFee / 100
+        // x = inputReserve, y = outputReserve
+
         // So by putting the values in the formulae you can get the numerator and denominator
+        // numerator = y * Δx = outputReserve * inputAmountWithFee / 100
+        // denominator = x + Δx = inputReserve + (inputAmountWithFee / 100) = [(inputReserve * 100) + inputAmountWithFee] / 100
+        // since both have 100 as base, we can remove it and thus:
+
         uint256 numerator = inputAmountWithFee * outputReserve;
         uint256 denominator = (inputReserve * 100) + inputAmountWithFee;
         return numerator / denominator;