Hi this is Rob.
I am going to show how to solve a quadratic
equation on the TI 84 Plus CE Graphing Calculator
by using the Polynomial Root Finder App on
the Calculator.
Let’s solve the following quadratic equation,
X squared + 2x - 8 = 0.
Press the apps key here, we want to use the
Polynomial Root Finder located at number 8.
Go down to number 8 here, press enter.
This is the Main Menu, we want to use number
1, Polynomial Root Finder.
Press enter.
These are the default settings for the Polynomial
Root Finder.
The only thing you may need to change is the
first one, Order.
This is the order of the polynomial, the order
is going to be equal to the highest exponent
of the x values of our equation.
In this case our equation is x squared + 2x
- 8 = 0.
The highest exponent on our x values is 2,
on the x squared.
So on this Poly Root Finder Mode, we need
to make sure 2 is chosen for Order.
It is.
All the other settings here are OK, but I
will briefly cover them.
The next line down, REAL, for real numbers,
we want this one for our equation, to the
right is a+bi for Complex Numbers, a complex
number is a real number plus or minus an imaginary
number.
If you know you are going to work with imaginary
numbers with your quadratic equations, then
you need to select this a+bi . If your order
of your polynomial is 4 or higher, you will
have no choice but to work with complex numbers,
for example go back up to Order and choose
4 as your Order.
See how Real is red lined out and the Complex
Number is highlighted.
I will change this Order back to 2 and go
back down to the Real line.
To the right of the Complex Number symbol
is re carrot theta i, this is the exponential
form of Complex Numbers.
The next line down is AUTO and Decimal, DEC.
The Auto mode should determine to give the
answer in a Fraction or Decimal.
The DEC will give the answer in a decimal
format.
The next line down, NORMAL, Scientific Notation,
and Engineering Notation.
Scientific Notation is a way of expressing
numbers that are too big or too small to be
conveniently written in decimal form.
For Quadratic Equations use NORMAL.
The next line down is the FLOAT.
Float is how many places past the decimal
point you want your answer to display.
The next line down is RADIAN or DEGREE.
Keep it on the default setting of DEGREE.
On the bottom of the window you see these
rectangle buttons or tabs, Main, Help, Next.
To access these buttons or tabs, they correspond
to the keys below in the first row.
Thus, this Main tab corresponds to this y=
key here.
And this Help tab corresponds to this trace
key here.
And the Next tab corresponds to this graph
key here.
Now we are ready to enter our quadratic equation,
go to the NEXT tab here by pressing this graph
key.
This screen pops up and this is where we enter
our equation.
The calculator shows a previous equation that
I was working with, to clear it out press
the CLEAR tab here by pressing this zoom key.
Our quadratic equation was X squared + 2x
- 8 = 0.
Our coefficient on the x squared is one and
we already have a one displayed so just press
the enter key.
Here we choose a plus or minus and our equation
is a positive 2x.
So press the enter key.
Here enter a 2 and press the enter key.
Here we need an minus 8, so press the minus
sign and press the enter key.
Enter our 8 and press the enter key.
Now we are ready to solve the equation by
going to the SOLVE tab by pressing this graph
key.
And there is the answer, x equals two and
x equals negative four.
From here if you want to enter another equation
to solve, then go to this coefficient tab
here by pressing this zoom key.
Now you can enter your next equation.
I am going to go back to the previous screen.
Going to this Store tab here will give you
different options of saving the information
of this equation.
Go to the STORE tab by pressing this trace
key here.
You can save the coefficients of this equation
to a LIST.
You can save the equation to the y= screen
so that you can see the graph the equation
later, or you can save the roots of the equation,
the roots are the answers we just calculated,
the x equals 2 and x equals negative 4.
The most common is to save the polynomial
to the y= screen.
So I will choose that one.
Highlight Store Polynomial to Y= and press
the enter key.
Here it stored the equation to the Y2.
Go to QUIT by pressing the y= key here.
I am going to get out of this Polynomial Root
Finder App and go to the y= screen.
To get out of this App, go to the Main Menu
tab by pressing the y= key here and then go
down to 6, QUIT APP and press the enter key.
Now we are back to the home screen.
Press the y= key.
There at y=2 is our equation.
We are going to graph it by pressing the graph
key here.
But when we press the graph key it will graph
the two equations that we have here.
The y1 will be graphed in blue color and the
y2, our equation, will be graphed in red.
And there is our equation graphed in red.
OK, that is it.
That is how to use the Polynomial Root Finder
App to solve a quadratic equation on the TI
84 Plus CE Graphing Calculator.
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