Posted by Zac on .
According to the rational root theorem, which is not a possible rational root of x3 + 8x2 x 6 = 0?

algebra 
Reiny,
verify that you meant
x^3 + 8x^2 + 6 = 0 
algebra 
Zac,
x3 + 8x2x6 = 0?

algebra 
Reiny,
x^3 + 8x^2  x  6 = 0
Let f(x) = x^3 + 8x^2  x  6
f(1) = 1+816 ≠ 0
f(1) = 1 + 8 + 1  6 ≠ 0
f(2) = 8 + 32  2  6 ≠ 0
f(2) = 8 + 32 + 2  6 ≠ 0
f(3) = 27 + .... ≠ 0
f(3) = 27 + 72 ... ≠ 0
numbers which are NOT possible rational roots are
±1 , ±2 , ± 3
Is that what you wanted? 
algebra 
Zac,
yeh but my homework has +2 and +1 as answers abd i can only choose one

algebra 
Reiny,
I used the 1 , 2, and 3 since they were factors of the 6 at the end.
There are an infinite number of choices of rational numbers which are NOT possible roots.
This is a poorly worded question.
go with the ±1 and ±2