If this is a perfect square trinomial, you want to look at your constant--36. the square root of 36 is 6, so your factors would be:
(x + 6)(x + 6) ... foil this, and see what your middle value is.
x² + 12x + 36 is your result. 12 is your middle term.
24 un the eighth row im sure of it because it adds my 3 each time if you look at the 1st row it says 15 then it adds by another 3 to 18 and then to 21