Update "cancellation of significant digits" example

Author: occar421

NumericalCalculation/BasicWithCSharp/CancellationOfSignificantDigits/result.txt

@@ -1,4 +1,5 @@
+f(x) = x^2 - 1000x + c = 0
 normal: x_1= 999.99900000, x_2= 0.00100708
-x_2 -> -0.00707901
+f(x_2) -> -0.00707901
 cared : x_1= 999.99900000, x_2= 0.00100000
-x_2 -> 0.00000006
+f(x_2) -> 0.00000006