# Thread: finding 2 zeros in an interval

1. ## finding 2 zeros in an interval

Hi

The question reads :show that the function f(x) =-x^5+4x^4-16x^3+12x+5 has two zeros in the interval (-2,0)"

With the intermediate theory I know that f(-2) is -59 and f(0) is 5 so we know there is one zero

But how on earth do you figure out if there is two????

from this Calculus beginner

2. Originally Posted by calcbeg
Hi

The question reads :show that the function f(x) =-x^5+4x^4-16x^3+12x+5 has two zeros in the interval (-2,0)"

With the intermediate theory I know that f(-2) is -59 and f(0) is 5 so we know there is one zero

But how on earth do you figure out if there is two????

from this Calculus beginner
are you sure you have the right function? this has only one real zero.

when you have the right function, you would show it has another zero the same way. find another point in (-2,0) in which the function changes sign. then you can apply the intermediate value theorem again to show there's another zero.

3. Here is the function.