In the Perdisco e-workbook, their approach to "annuities due" questions differ to the one shown in our textbook.
Yes and no, the perdisco involves working out the present value with an ordinary annuity and forward dating it, however, they are the same thing and both formulas will simplify to each other.
The two approaches produce different answers to each other.
Really, there's no other way I can put it but to say that you are 100% wrong.
The equation given on page 47 of the finance textbook, equation (2.12), can be manipulated to give the Perdisco equation. I just did it right then, to make sure.