PROGRAMMING THE TI

C. Regena

Algebra Tutorial

Part 1

We have examined educational software in previous columns and discussed how to construct drill programs. Now let's create a tutorial program. There have been a lot of requests for an educational program for algebra so here is the first part of a tutorial program on multiplying binomials.

"Algebra Tutorial," assumes the student has some knowledge of algebra and understands terms usually introduced before binomial multiplication. This program only covers multiplication of one binomial (numeric expression of two terms) by another binomial—such as (x + 5) times (x + 4). Additional related units could include multiplying polynomials, dividing polynomials by binomials, and factoring trinomials.

The program uses PRINT statements to avoid DATA statements with lots of numbers. If you prefer to prevent scrolling, you can use the graphics method of CALL HCHAR and CALL VCHAR to print problems on the screen.

Redefining Characters

Lines 160 and 170 redefine two characters for use in printing the problems. Character 94 is ordinarily the caret or exponentiation symbol, but is redefined here as a 2, which will be used as the superscript for a number squared. To type the program in, use SHIFT 6 to get the ^ symbol in lines such as line 400.

The underline is also redefined. Character 95 is ordinarily the underline, but several underlines together yield a dotted line, and we want a solid line. Lines 230 and 270 are examples of the underline in the listing. To type the underline, press the FCTN key and the U. As you type the listing, you will see the regular symbols, but when you run the program, you will see the redefined characters.

When learning algebra, it is important to understand that you can work with letters using the same rules and methods that are used with regular numbers. Lines 190–300 print a screen showing a comparison of binomial multiplication in algebra with a numeric multiplication problem. Lines 310–460 show the general form of the multiplication problem and its answer.

Generating A Random Problem

Lines 470–950 present a problem for the student to try. A and B are two random numbers chosen for the second terms of the binomials. This problem is the simple case using X plus a number from 1 to 3. The computer goes through the problem step by step, and the student presses a number where prompted. Correct numbers must be entered to continue.

CALL KEY is used rather than INPUT, so the student just needs to press a key for the answer. If you use INPUT, there is a greater chance for user error or for the program to crash. Avoid INPUT in tutorials so the student can use the program as easily as possible.

The tutorial adds new information a little at a time. Lines 960–1110 present a screen showing numeric coefficients for the first term. Lines 1120–1180 (and the subroutine starting at line 1960) give the student a problem of this type. Lines 1190–1300 present a screen of information about using positive and negative numbers.