Type the coordinates of two points and this program gives you the slope of the line through them, along with its equation in y=mx+b form.
Send it to your calculator
Plug the calculator into your computer with a USB cable, then use the button below.
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Open it on the calculator
Press the prgm key, in the middle of the keyboard a couple of rows below the arrow keys.
The PROGRAMMING menu opens with TI-Basic already highlighted. Press enter.
SLOPE is in the program list. Press enter to pick it, which puts prgmSLOPE on the home screen, then enter again to run it.
Find the slope and the equation
The program asks for four numbers one at a time: the x and y of your first point, then the x and y of your second point.
Type each coordinate and press enter after it, using the (-) key for a negative. For the points (1, 2) and (3, 8), the moment you enter the last number it answers Slope=3 and y=3x-1.
Good to know
- It's the slope formula, worked out for you. The program computes (y₂ − y₁) / (x₂ − x₁) for the slope, then works back to the y-intercept so it can write the whole equation. If you want the straight-line distance between the same two points instead, the Distance Formula program takes the same four coordinates.
- Vertical lines get caught. When both x-coordinates match there is no slope to compute, so the program answers "Undefined (vertical)" instead of dropping you on an error screen.
- The equation comes out tidy. A horizontal line gives y=3 rather than y=0x+3, and a line through the origin gives y=3x rather than y=3x+0.
- Answers that aren't whole come out as decimals. The points (1, 1) and (4, 3) give Slope=0.6666666667 and y=0.6666666667x+0.3333333333, not the exact thirds.
- Negative coordinates work. Type them with the (-) key, not the subtraction key. Points (2, 7) and (5, 1) give Slope=-2 and y=-2x+11.
- Rerun it with one keypress. Pressing enter on the home screen repeats whatever you ran last, so right after a run a single enter starts a fresh set of prompts.
- A calculator reset removes it. TI-Basic programs live in RAM, so if the program disappears after a reset, just send it again from this page.
