• Don’t plot less than three nor more than 1000 points.
• Be sure that your x min and x max DO NOT include values that will result in y values that are non-real numbers.
• For example, if you wish to graph y = the square root of x, you would enter sqrt(x) in the expression box, but you would also need to change the x min to “0.” The use of any negative numbers for x will result in an “invalid expression.”
• For example, if you wish to graph the circle:

x 2 + y 2 = 4, which is not a function, you need to create two separate functions: the top of the circle and the bottom of the circle. Graph: y = sqrt(4-x^2) in Data 1 and y = -sqrt(4-x^2) in Data 2, but you need to be sure that your x min is –2 and your x max is 2 (the positive and negative square roots of 4).

• Solving Systems of Equations Graphically
• The AGC has a tracer function like other graphing calculators (ALT- right arrow ), which verbalizes the coordinates of each point as you trace. However, it doesn’t voice when you have reached a point of intersection for two graphs displayed at once. When graphing a system of equations (two data sets), go to the Plot Tab Page, Section “Source,” and select “Difference (1-2).” Then press Alt-0 to find the approximate x-value(s) of the point(s) of intersection. Then go to the data table of either or both equations and search for the y-value(s) associated with the x value(s) you have determined. You will now have the approximate coordinates for the point(s) of intersection (if any exist).
• Another alternative is to print the graph of the system to a Tiger graphics embosser (or print it to a print printer with Braille font, copy onto swell paper, and run through a tactile imaging machine if you don’t have a Tiger). Then determine the point(s) of intersection(s) (if any exist) from the hard copy graph.
• Unless the point of intersection is a pair of integers, graphing isn't the best method of solving systems. Even then, most graphing calculators don't give you the correct answer, only an approximation. Instead of giving you the solution of (1, 4), they might indicate (1.012, 3.998) for example.
• Solving Systems of Equations Symbolically
• Shortly after learning the graphing method, students learn how to solve systems of linear equations using substitution, linear combination, and matrices. Since the AGC will do matrices, I give you the following example.
• If you had the system:
3x - 5y = -7
5x - 8y = -11
Go to the matrix tab. Type INV[3,-5;5,-8] (Note this is using the coefficients of the variables.)
It will give you the inverse of that first matrix: [-8,5;-5,3] or something fairly close.
Then, you would multiply that last answer by the matrix

[-7;-11] (constants on the right side of each equation) and the answer will pop out as: [1;2].
This solution matrix shows you that the answer is (1, 2) or the point of intersection.