the quadratic formula programming problem

I see two issues with your code.

1. You’re using B, not -B
2. You’re doing /2*A, not /(2*A). The ti83/84 family of calculators evaluates multiplication and division strictly from left to right. So /2*A is “divide by two, then multiply by A”.

I would cleanup your code as follows:

Prompt A,B,C
B²-4AC→Z
Disp "DISCRIMINANT:", Z

-B-√(Z)→Y
-­B+√(Z)→X
X/(2A)→D
Y/(2A)→E
Disp  "X:",D,E