Question

Determine the zeros of f(x) = x4 – x3 + 7x2 – 9x – 18.

Answer 1

I don't understand how to do this one @phi

Answer 2

± factors of 18: ± 1,2,3,6,9,18

so try and see if you can find a root

Answer 3

2

Answer 4

now do synthetic division

Answer 5

x^3+x^2+9x+9=0

Answer 6

yes, now try to find a root for this using
±1,3,9

Answer 7

-1

Answer 8

sy

Answer 9

ok, now syn div on the cubic

Answer 10

okay

Answer 11

x=+/-3

Answer 12

almost

you should have gotten
x^2 +9 = 0

did you ?

Answer 13

yeah

Answer 14

*x=+/-3i sorry

Answer 15

then
x^2= -9

now as you know, there is no real number that when you square it is *negative*

Answer 16

yes, looks good