Here's another Quadratic formula: This one finds X and checks it to see if it works in the equation, if it doesnt work it displays an X. :Lbl 7 :ClrHome :Disp "AX(2)+BX+C=0" (2) means "squared" :Disp "A=" :Input A :If A=0 :Goto 7 :Disp "B=" :Input B :Disp "C=" :Input C :(-B+$(B(2)+-4AC))/(2A)->F $ means "square root" :(-B-$(B(2)+-4AC))/(2A)->G :A(F(2))+BF+C->T :If T=0 :Goto 1 :If T<>0 :Goto 2 :Lbl 5 :A(G(2))+BG+C->Y :If Y=0 :Goto 3 :If Y<>0 :Goto 4 :Lbl 1 :Disp F :Goto 5 :Lbl 2 :Disp "X" :Goto 5 :Lbl 3 :Disp G :Stop :Lbl 4 :Disp "X"