The answer is A; a=50t cause if you were to put 0, you would get 0 which is the first point, if you put in 1 you get 50, if you put in 2 you get 100 and so on.
The pattern is: ( a - b )² = a² - 2 a b + b² ( square of last term of binomial - the missing term) x² - 2 · 8 · x + 8² = x² - 16 x + 64 = ( x - 8 )² The missing term is: 64