Question

Using Descartes Rules of Signs what is the positive zeros and negative zeros for f(x)= x ^3 -x^2-6x-70

Answer 1

http://www.purplemath.com/modules/drofsign.htm

Answer 2

http://www.youtube.com/watch?v=5YAmwfT3Esc

Answer 3

Can you help, a little bit.

Answer 4

Why don't you tell me the part you don't understand?

Answer 5

Sorry, I'm cooking.
@dumbsearch2

Answer 6

@Mertsj

Answer 7

Descartes Rule of Signs does not tell what the positive and negative roots are...it only tells the possible number.

Answer 8

So if you reread your question you will see that you have posted it incorrectly.

Answer 9

I am asked the number of sign changes and what are the positive zeros

Answer 10

I put 1 sign changes, and it says to subtract 2

Answer 11

if possible

Answer 12

Next it asked for sign changes in P(-x) and the negative zeros

Answer 13

There is 1 sign change so the maximum number of positive roots is 1

Answer 14

and again subtract 2 and how many negative zeros it has.

Answer 15

The rule says the number of positive roots is the number of sign changes or less by a multiple of 2.

Answer 16

P(-x)=-x^3-x^2+6x-70
So the number of negative roots is 2 or less by a multiple of 2

Answer 17

To find the positive root, use synthetic division using the positive factors of 70 as the shelf numbers until you find one with remainder 0. That will be your positive root.

Answer 18

Ok so use -70 for synthetic on the P(x)?

Answer 19

Use the positive factors of 70

Answer 20

Since you are trying to find the positive root.

Answer 21

Ok and this is for P(-x)

Answer 22

No. You are trying to find the positive root of the original function.