Question

I’ve got the following Visual Basic code:

    Dim L16, L23, L45, t As Double
    Dim LBase, LAdjacent, LOpposite As Double

    L16 = 20
    L23 = 10
    L45 = 30
    t = 1

    LBase = L16
    LAdjacent = L23
    LOpposite = L45

    Dim Sum As Double

    Sum = t ^ 2 * L16 + 6 * t ^ 3 + 2 * L16 ^ 3 + 3 * L16 ^ 2 * t + 2 * L23 ^ 2 * L16 + L23 ^ 2 * t + 8 * L23 * t * L16 + 4 * L23 * t ^ 2 - L45 ^ 2 * L16 + L45 ^ 2 * t - 4 * L45 * t * L16 + 4 * L45 * t ^ 2

    Console.WriteLine("1st Sum: " & Sum)

    Sum = t ^ 2 + LBase + 6 * t ^ 3 + 2 * LBase ^ 3 + 3 * LBase ^ 2 * t + 2 * LAdjacent ^ 2 * LBase + LAdjacent ^ 2 * t + 8 * LAdjacent * t * LBase + 4 * LAdjacent * t ^ 2 - LOpposite ^ 2 * LBase + LOpposite ^ 2 * t - 4 * LOpposite * t * LBase + 4 * LOpposite * t ^ 2

    Console.WriteLine("2nd Sum: " & Sum)

Both equations should be equivalent: I’ve simply replaced L16 with LBase, L23 with LAdjacent and L45 with LOpposite. Yet the first equation outputs 3586 while the second outputs 3587. Why?

I’m using VS2010

Amr

Answer 1

First Sum calculation:

Sum = t ^ 2 * L16 + ...

Second Sum calculation:

Sum = t ^ 2 + LBase + ...

One has *, where the other has + .