Rem derivative for y= a*x^2+b*x+c

a=-1:b=-3:c=1

for y = -5 to 5 : for x = -5 to 5

circle int(30*x)+150, int(30*y)+ 150,2

next x : next y

line 150,0,150,300 : line 0,150,300,150

color red

for x = -5 to 5 step .1

y = a*x^2+b*x+c

circle 30*x +150, 150 - 30*y,2

next x

input "What is the derivative",r$

for x = -5 to 5 step .1

dy=((a*(x+.1)^2+b*(x+.1)+c)-(a*x^2+b*x+c))/.1

circle 30*x +150, 150 - 30*dy,2

next x