1/2 + 2/5 = 5/10 + 4/10 = 9/10
this formula, doesn't rely on a product, relies on a "sum", or is namely an arithmetic sequence, aₙ₋₁ -3 is another way of saying, the value of the previous term minus 3, so it relies on the ordinal value of a term, so is an recursive formula, well, let's get it when n = 4.

In order to find this you need to find a common denominator. 2/3 and 3/4 common denominator would be 12 and so what you do to the bottom you must do to the top. 2x4 is 8 and 3x3 is 9. that would make 8/12 and 9/12. 8 plus nine is 17 and 12 stays there so the answer is 17/12 which equals 1 and 5/10.
That equals <u>.0124031008</u>