15 4 – 5: Locating Zeros of a Polynomial Function So far, all of the methods we’ve used to find zeros/roots/solutions will only find those that are rational. This means they must be whole numbers or fractions. But what if the roots are irrational? For example: x = When finding zeros by hand, we can only estimate irrational zeros by finding which numbers they fall between. 1. Determine between which consecutive integers the real zeros of the function f(x) = x 3 – 4x 2 – 2x + 8 are located. By Hand: By Calculator: x 1 -4 -2 8 -3 -2 -1 0 1 2 3 4 5 CALULATOR TIP: To get a more accurate answer, you can change the interval on the table on your calculator or use the CALC feature 2:Zero.