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Question
I am trying to solve quadratic equations in VBScript. But, the results seem incorrect at times. What can I do?
Answer
Most likely, the problem that you are experiencing are floating point rounding errors. Being that you only get 15 decimal places of accuracy, you can use them all up if you are dealing with small numbers.
The following algorithm should produce more accurate results:
Function QuadraticSolver(a, b, c)
Dim d, s0, s1
d = b * b - 4 * a * c
If d < 0 Then
' No real solution
QuadraticSolver = Null
Else
s0 = (-b - Sqr(d)) / (2 * a)
s1 = (-b + Sqr(d)) / (2 * a)
If Abs(s0) < Abs(s1) Then s0 = s1
s1 = c / (a * s0)
QuadraticSolver = Array(s0,s1)
End If
End Function