quadineq.82p - From the Spring 1996 issue of Eightysomething!





Graphing Quadratic Inequalities

Program by Krissy Couture

Edited by Nils Ahbel



Krissy Couture is a sophomore at Bellows Free Academy in St. Albans,

Vermont.  At the beginning of last year her mother won a TI-82 in a drawing

at her school’s Mathematics Department Calculator Open House.  Since then,

Krissy has become very proficient at programming the TI-82.  Her teacher,

Mr. Berthiaume, challenged her to create a program to graph quadratic

inequalities.  Her results are given below.



The program allows you to graph not only Y=AX^2+BX+C, but also Y>, Y , Y<,

and Y  AX^2+BX+C.  For inequalities, the graph is displayed in two steps.

First, the boundary of the graph of the inequality is displayed, dotted <

and >, and solid for >= and <=.  Second , the shaded region is filled in.

It then displays the axis of symmetry, the coordinates of the vertex, the

x-intercept, and the y-intercept(s) if they exist.  Display screens for

Y>2X^2-3X-9 are given below.



...

Thanks to Laura Gonyeau for submitting the program!