Posted by Chopsticks on Tuesday, January 13, 2009 at 12:32am.
If someone looks at this, please reply. I will for replies around 6:30am before school starts.
If the rational root is p/q, then p must be a divisor of 30 and q a divisor of 2.
Also, if there are many possible candidates like in this case, you should not try them all out. Instead, you should proceed as follows.
Let's denote the polynomial by P(x).
Suppose y is a possible rational root. But then we check if y is a root and see that P(y) is not equal to zero. You can then apply the Rational Roots Theorem to the polynomial:
Q(x) = P(y + x)
You don't have to actually replace x by y + x in the original polynomial and expand out all the powers. All you need to know to apply the Rational Roots Theorem are the coefficients of the highest power and the constant term.
The coefficient of the highest power of x remains the same, the constant term is P(y).
In this case, if you take y = 1, then
P(y) = 32. So, the possible rational roots of Q(x) are of the form plus or minus 2^n for n ranging from minus 1 to 5. Therefore the possible rational roots of the original polynomial are of the form:
1 plus or minus 2^n
You then check which of the rational root candidates on your original list are of this form. You are then left with:
x = 1/2, 3/2, -1, 3, -3, 5, -15.
If we check x = -1, we find:
P(-1) = 42.
This then generates the following candidate roots:
x = -1 + p/q
with p a divisor of 42 and q a divisor of 2. The remaining candidates are then:
x = -3 and x = 5.
None of them work, so there are no rational roots (provided I didn't make any mistakes :) )
give more example by solving rational zero theorem.
Precalculus - I'm HOPING this is the last problem I need help on.. :-/ List ...
College Algebra - Use rational root theorem and the factor theorem to help solve...
Pre Calculus - 1. Find all rational zeros of the polynomial. Then determine any ...
Algebra - Using rational zero theorem find all rational zeros P(x)=3x^3+43x^2+...
Pre-Calculus - Rational Functions y = (x^2+7x-4)/(x-2) Since the degrees of both...
Math - how do you solve this problem??? Write each rational number in the form a...
Algebra - Can someone please explain how to do these problems. 1)write a ...
algebra - use the rational zero theorem to list the potential rational zeros of ...
math - Use the rational zero theorem, Descartes rule of signs, and the theorem ...
Calculus - Show that the function f(x)= x^(3) +3/(x^2) +2 has exactly one zero ...
For Further Reading