p(x)=5x^3-4x^2+20-16

use synthetic division to show that x=2i is a zero of p(x)

2 answers

Your function, which I will assume was to be
p(x) = 5x^3 - 4x^2 + 20x - 16 , factors very nicely by grouping

p(x) = 5x^3 - 4x^2 + 20x - 16
= x^2(5x-4) + 4(5x-4)
= (5x-4)(x^2 + 4)

so the zeros are
x = 4/5 and x = ± 2i

Using synthetic division for this expression is totally out of place.
lim x�¨�‡ 2x 3 +5x 2 −x 3 =