In your formula why do you use the exponent of 2 and none for year two of the last year with the cost I figured it would be ^3 for the initial investment then ^4 then ^5 at the end because the initial investment is the third year then the next two years are the fourth and fitth
Are you talking about the irr formula? I do see that I made a slight error. The -0.5 comes a year after the last cash inflow I guess. That generates an ugly cubic. I probably misread the problem because I thought that they would give you a reasonable equation to solve.
The point is that you can start the irr calculation at any date. It always simplifies to the initial cash flow being discounted by (1 + r)^0, which equals 1.
If we start it now, we have, as you thought,
[MATH]\dfrac{0}(1.11^0} + \dfrac{0}{1 + r)^1 + \dfrac{-\ 3}{(1 + r)^2} + \dfrac{2}{(1 + r)^3 + \dfrac{2}{(1 + r)^4} + \dfrac{-\ 0.5}{(1 + r)^5} = 0 \implies[/MATH]
[MATH]\dfrac{-\ 3}{(1 + r)^2} + \dfrac{2}{(1 + r)^3 + \dfrac{2}{(1 + r)^4} + \dfrac{-\ 0.5}{(1 + r)^5} = 0 \implies[/MATH]
[MATH](1 + r)^2 * \left ( \dfrac{-\ 3}{(1 + r)^2} + \dfrac{2({(1 + r)^3 + \dfrac{2}{(1 + r)^4} + \dfrac{-\ 0.5}{(1 + r)^5} \right ) = (1 + r)^2 * 0 \implies[/MATH]
[MATH]\dfrac{-\ 3}{(1 + r)^0} + \dfrac{2({(1 + r)^1} + \dfrac{2}{(1 + r)^2} + \dfrac{-\ 0.5}{(1 + r)^3} = 0.[/MATH]
That is where I would normally start. That leads to
[MATH](1 + r)^3 * \left ( \dfrac{-\ 3}{(1 + r)^0} + \dfrac{2({(1 + r)^1 + \dfrac{2}{(1 + r)^2} + \dfrac{-\ 0.5}{(1 + r)^3} \right ) = (1 + r)^3 * 0 \implies[/MATH]
[MATH]-\ 3(1 + r)^3 + 2(1 + r)^2 + 2(1 + r)^1 - 0.5 = 0.[/MATH]
Now you can solve that by using the cubic formula, the Newton-Raphson method, or excel.
The answer I get from excel is r approximately equals 12.7%.
Let's check..
[MATH]\dfrac{-\ 3}{1.127^0} +\dfrac{2}{1.127^1} + \dfrac{2}{1.127^2} + \dfrac{-\ 0.5}{1.127^3} \approx 0.[/MATH]
I have to tell you that I have never thought that the irr calculation makes much sense. It's not the math that is at fault; it is the economic assumption behind it. The fact that it may give multiple answers should be enough to indicate that it has little to do with reality. Of course, you have to learn it to pass. Then you can forget all about it.