# Thread: Finding the rational roots

1. ## Finding the rational roots

I'm kind of stuck on these problems and would appreciate some help.
Also is there a way to find the rational roots on a Ti-84 graphing calculator?

The problems that I have trouble with are...
X^2-16=0
X^3-15X+22=0
X^4-7X^3+13X^2+X-20=0
X^4+5X^3+3X^2+45X-54=0
2X^4+X^3-22X^2+29X+20=0
X^4-4X^3+7X^2-6X=0
6X^3-31X^2+3X+10=0
X^3-X^2-3X+2=0
4X^3-8X^2+X+1=0

2. Originally Posted by Rainy2Day
I'm kind of stuck on these problems and would appreciate some help.
Also is there a way to find the rational roots on a Ti-84 graphing calculator?

The problems that I have trouble with are...
X^2-16=0
X^3-15X+22=0
X^4-7X^3+13X^2+X-20=0
X^4+5X^3+3X^2+45X-54=0
2X^4+X^3-22X^2+29X+20=0
X^4-4X^3+7X^2-6X=0
6X^3-31X^2+3X+10=0
X^3-X^2-3X+2=0
4X^3-8X^2+X+1=0

the first one x^2 - 16 is a difference of squares question
if you are able to square root both terms AND they are being subtracted from one another you can write it like this

x^2 - 16 = (x - 4)(x + 4), and x = 4, x = -4

for the cubics (the ones that have 3rd degree or highest power is 3, ex the last in the list), check out this video

Solving cubics

you could use the calculator to graph the functions and then see if it tells you the X intercepts

its probably easier to not use the calc though hehe

3. Thank you