This complete statement must be memorized, and does frequently occur as a question on tests.  Only the complete statement, in its full logical 'if-then' form, will be given credit.

Important Note:  It follows from the Quadratic Theorem that if you have an equation of the form

a t^2 + b t + d = f,

you can subtract f from both sides and get the equation into the form a t^2 + b t + c = 0. 

Only in this form does the quadratic formula apply.