One of the most useful programs you can have in your TI calculator is the Quadratic Formula.

During this tutorial, I will teach you how you can do your own program to calculate the solutions of any equations of the following type:

ax^{ 2 }+bx+c=0

First, we need to get a, b and c values from user. To achieve this we will use some **Input** instructions preceded by a **ClrHome** one, that tells the processor to clear the screen.

```
ClrHome
Input "A=",A
Input "B=",B
Input "C=",C
```

These “inputs” retrieve the values from the user and store them in the variables A,B and C.

Then we will clear the screen once more and add some **Disp “”** instructions that will be discussed later.

```
ClrHome
Disp ""
Disp ""
Disp ""
Disp ""
Disp ""
```

Now it’s time to do the intermediate step:

\dfrac { -b\pm \sqrt { { b }^{ 2 }-4ac } }{ 2a }

We will use **Output** instructions to display text and variable values to a specific place on the screen:

```
Output(1,1,B)
Output(1,5,"+/-")
Output(1,9,"√(")
Output(1,11,B²-4AC)
Output(1,16,")")
Output(2,1,"----------------")
Output(3,8,2A)
```

And finally we check if the equation has solutions by checking if the following inequation is true:

{ b }^{ 2 }-4ac\ge 0

If it is true, then we can print the solutions. However, if it has no solutions, we should print an error message like “NO ZEROS FOUND”. The **Then** and **End **instructions mark the beggining and the end of a block, which means that if the condition is true, all the instructions before the **Else **will be executed and if it is false it will only execute the instruction between **Else** and **End**.

```
Output(4,1,"ZEROS:")
If (B²-4AC)≥0
Then
Output(5,1,(B-√(B²-4AC))/(2A)
Output(6,1,(B+√(B²-4AC))/(2A)
Else
Output(5,1,"NO ZEROS FOUND"
End
Output(5,12," "
Output(6,12," "
```

The last **Output** instructions limit the solution digits presented.

To conclude, we should note that the previously used **Disp “”** instructions just tell the processor to print **Done** in a specific place in the screen.

Here you have the full code:

```
ClrHome
Input "A=",A
Input "B=",B
Input "C=",C
ClrHome
Disp ""
Disp ""
Disp ""
Disp ""
Disp ""
Output(1,1,B)
Output(1,5,"+/-")
Output(1,9,"√(")
Output(1,11,B²-4AC)
Output(1,16,")")
Output(2,1,"----------------")
Output(3,8,2A)
Output(4,1,"ZEROS:")
If (B²-4AC)≥0
Then
Output(5,1,(B-√(B²-4AC))/(2A)
Output(6,1,(B+√(B²-4AC))/(2A)
Else
Output(5,1,"NO ZEROS FOUND"
End
Output(5,12," "
Output(6,12," "
```

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