The quadratic formula solves any equation shaped like ax² + bx + c = 0, but keying the whole thing in by hand, with the square root and the negative sign and everything divided by 2a, is exactly where a wrong answer sneaks in. This program does the keying for you: type the three numbers a, b, and c, and it prints both solutions.
Send it to your calculator
Plug the calculator into your computer with a USB cable, then use the button below. It takes a few seconds, and there's no code to type in.
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Open it on the calculator
Press the prgm key. It sits in the middle of the keyboard, two rows below the arrow keys.
The PROGRAMMING menu opens with TI-Basic already highlighted. Press enter.
QUAD is in the program list. Press enter to pick it, which puts prgmQUAD on the home screen.
Solve a quadratic
Press enter to run it. The program prints the standard form AX²+BX+C=0 as a reminder of what each letter stands for, then asks for the first coefficient with an A? prompt.
Type the three coefficients from ax² + bx + c = 0, pressing enter after each. For x² − 5x + 6, that's A = 1, then B = −5 (use the negative key, just left of enter, for the minus), then C = 6. The moment you enter C, it lists both solutions, labeled so you can read them off at a glance: X = 3 and X = 2.
To solve another one, just press enter on the home screen. The calculator reruns the program and the A? prompt comes right back.
Good to know
- It's the quadratic formula, worked out for you. Behind the scenes the program evaluates x = (−b ± √(b² − 4ac)) / (2a) from the a, b, and c you type, so you get both roots without keying that whole expression in by hand.
- A repeated solution shows up twice. x² − 4x + 4 has the one solution 2, so the program prints X = 2 and X = 2. That doubled answer is your signal the parabola just touches the x-axis at a single point.
- No real answer, no error screen. When the part under the square root comes out negative there are no real solutions, and the program says so plainly instead of dropping you on an error screen.
- Enter 0 for A and it isn't a quadratic. With no x² term the formula would divide by zero, so the program answers "Not a quadratic" rather than erroring out.
- 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.
